1. The first and most frustrating thing is thinking it's a pet breeding sim, but finding out that it's just pet collection/clicking.
2. Finding a bunch of "loose ends," like unfinished features, that remain unfinished, because the staff is working on far too many things at one time.
3. Being misled into thinking there might be a bunch of interesting features, but finding out that it's just one feature that's been copy/pasted fifty thousand times, with different rewards (I'm talking about Flight Rising's "holidays" here, specifically.)
4. Sites that incorporate social media to the point that they tie social media into contests and staff-run games (Wajas in particular is very guilty of this.)
5. Sites that charge an astromical amount of real-world money for custom things and changing the amount of money they expect to be paid for custom orders. (Celestial Equine is extremely guilty of this)
6. Sites that rely heavily on Cash Shop stuff. despite offering Premium memberships (Celestial Equine is extremely guilty of this.)
7. Sites that are so worried about being "politically correct" that they effectively neuter aspects of their own site (Flight Rising is guilty of this, with what they've done to the Plague flight, among other things.)
8. Sites that look like they might end up being very interesting, but just end up being glorified, yet censored RP forums with nothing else to do and giving players no reason to stick around. (Mycena Cave.)