Generally dangerous seems disingenuous. I think it's generally practical to assume most people are decent human beings. It's worked very well for me over time (and clearly has worked for services like uber, lyft, ebay, craigslist, airbnb, etc), but it when bad actors appear (as they always do once you hit a certain number of persons involved), it's what happens then that counts the most.
I think E-bay has tended to handle things very well, I haven't heard many horror stories about them (if ever), and they've been around for quite some time (as software companies go) and quite successful. Uber and AirBnB on the other hand I've heard plenty of horror stories from. It may (or may not be) the reason I've not used Uber in months and months and have only ever booked a room once on AirBnB (which I cancelled last minute and still paid for).