Firstly I spent weeks chasing down what I thought was a data loss bug in iCloud. After much effort I managed to reproduce it. Turned out it was an issue with TeXshop rather than iCloud.
Secondly, the one time I had a photo lost, it wasn't lost. I just couldn't find it in the 12000 photos I had. It wasn't where I'd left it.
The third one was a data loss bug, was reproducible, was reported to Apple and was fixed. This was due to how Numbers handles three devices and how it decides the winner of a conflicting change and was an edge case as number 1 awkward customer.
YMMV but user testimony may be as reliable as eyewitness reports.