Depends on the fan I suppose, and conditions. Smoking and vaping near a PC has effects on plastics. I've seen the results of quite a few GPU fan blades break with a vacuum clean. But they do tend to be thinner and closer to a higher heat source. Could be as simple as getting the fan spinning and touching it with the vacuum cleaner that snaps the blade rather than the spin itself.
The voltage thing is certainly true. You can test that with a simple multimeter. Whether the motherboard has a reverse bias diode in place to protect itself is another matter. Not sure about PWM fans though, that would be something to test.
Quality of the fan will matter a lot. Some cheap fans are pretty weak at the hub/blade connection and more prone to snapping. Thinner blades at higher RPMs then designed can stretch out and impact the fan frame.
A fan designed for 1500 RPM will react differently then one designed for 6000 RPM. A good ball bearing fan is probably fine. Some the cheaper sleeve bearing fans would be more prone to damage. A static pressure fan vs an airflow fan will act differently. And the more typical hybrid fans of today will be different.
Age of the fan and its current bearing status is worth considering. If the fan already has a wobble, over spin might claim it. People aren't generally cleaning shiny brand new parts.
Personally never happened to me, but then I don't let the fans spin while cleaning. It is a simple precaution. I tend to disassemble and hand clean everything, and I make good use of case filters. (I used to have long hair, and now I have a cat)
Since I have been buying higher quality components these last fifteen years or so, also hard to judge the average 5 dollar case fan. I still occasionally buy a pack of the cheapest Cooler Master fans for general use, but they don't see much in the way of 24/7 operation.