I've accidentally killed power to the C7 several times without any ill effects. There must be certain time or function where losing power will corrupt the unit. What are the odds?
The likelihood of database corruption because of an interrupted write is raised with an abrupt power outage. Before I put my hubs on a UPS, I think I experienced a corrupt database once. And it was soon after I installed the first hub.
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While not answering you C7 specific need, what made me realized I needed a UPS beyond possible corrupt database was in keeping the "time" right on my hub, not missing time-based events, even if my internet goes down, as well as I have my router on a UPS to prevent any smaller blips from killing my mesh router which takes a while to re-connect across hubs.
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Well, if the product requires a UPS then I will go out and buy one. But I can't find any mention or warning in the documentation that a UPS is required/should be used.
In an ideal world there are no power interruptions. Some locations deviate from that ideal more than others.
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You won't find one on a PC either but you constantly lose power on a PC and you'll get corruption there too...
Lots of small UPS's available. Something like this would work fine. https://www.amazon.com/TalentCell-Uninterrupted-27000mAh-Wireless-Smartphone/dp/B07WLD32RP/ref=sr_1_5?keywords=usb+ups&qid=1652125632&sr=8-5
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That's because you don't need a UPS if power never gets interrupted. 
If you can do it, however, I think it's a good idea. There are notes in the documentation that you should always try to shutdown properly rather than just pulling power, and that applies whether it's you or nature (or the electric company) doing it. See the Care and Maintenance doc for more tips.
It is important to remember that your Hubitat Elevation hub is a computer and should be treated as such. This means you must shut down your hub down safely using Shutdown Hub from the Settings page, [...]
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You can spend much less money. The hub's power draw is so low that all you need is an external battery that supports pass through charging. I use this one in my own setup:
Voltaic Systems V25 6,400mAh USB Always On Battery Backup Power Bank for iPhone, iPad, Samsung Galaxy, Android, and HTC Devices (Gray) https://www.amazon.com/dp/B07ZS3WYZY/ref=cm_sw_r_apan_i_14A11DZQ4YTZG6SBKMGK?_encoding=UTF8&psc=1
That will give you plenty of time to log in and do a clean shutdown if you lose power.
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Database issues rarely happen when the power is suddenly cutoff while the data is being recorded in the hub's database tables. The more active the hub is, the higher the risk is that one of those power outages will cause the database to become corrupted.
When that happens, is not the end of the world. There is always the option of performing a Soft Reset followed by a backup restore. If you have frequent power outages, putting the hub on a UPS is a good idea, and so is Shutting Down the hub properly from Settings, before cutting the power off.
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I have 4 CyberPower UPS that I bought at Costco. I have my hubs, router, AT&T gateway, and 2 PCs on them. The best thing is having WiFi for hours and the ability to charge phones if the power goes out. I also have a Homepod mini on one.
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I think any electronic will benefit from a ups. Aside from the battery backup they can also do some power conditioning to ensure good voltage is always provided to the device.
The big problem I have is there is a lack of good quality small UPS devices. The hubitat and network gear don't really need much power in most homes. The thing is it is hard to find anything that is priced well for this use other then a small computer UPS.
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Where I live, we rarely have significant power outages, but we occasionally do have blips in the incoming voltage. One of the features of a UPS is that they have excellent protection against voltage spikes. They won't protect your equipment if lightning strikes nearby, but they will protect against most lesser spikes. Even the startup of a central air conditioner system can cause a voltage spike. I have occasionally had a UPS go to battery backup when the voltage goes above or below the safe range, even if only for a few seconds.
I use USP devices on my computers, cable modem, router, VOIP phone adapter, and home automation hubs. I do not use them on individual mains powered automation devices.
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Agreed. Since getting two UPS for a few different uses, I've actually noticed my power goes out (flickers) more often than I thought. I can hear the UPS beep/clicks where normally I may have faulted a bulb depending on where I was in the house.
Typically due to high wind on occasion where I live.
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I have an APC450 UPS. I noticed short "clicks" of the relays seemingly responding to an "outage". I concluded the APC circuit is super sensitive in order to allow the power transfer to not allow a dropout.
In such cases the filtering in my PC power supply, router and Hub easily carry the devices through such a blip.
However it does give one a warm feeling that the UPS is "on the job" 
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I was under the impression that brownouts can be just as bad as a full outage maybe worse in some instances.. so a "Line-Interactive" UPS might be worth it.
Some links for posterity:
Very true of SMPS's. I use old PC PSUs to power stuff including a 3d printer. A brownout once killed the PSU during a print run because of specific characteristics of this type of PSU - when the input falls the PSU attempts to maintain the output by drawing more current up the point where the unit can (and did in my case) fail.
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I have heard a number of predictions of power grid brownouts in many areas this summer. When voltage drops, generally the power output will drop, which is what the power company hopes will happen. This can be quite stressful on power supplies as the device may try to maintain power at the lower voltage, resulting in a higher current draw. Thus, a UPS is designed to go to standby power not only when there is a power outage, but when the voltage drops to an unacceptable level.
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