Yes. It is important to note that the way these sites essentially operate is by word of mouth very quickly and by reporting. What drives the sales of apps is the fact that people will comment on the apps and rate them.
We call “vapourware” any app that's been produced and is out there but doesn't mean anything and doesn't work. Essentially, the first couple of buyers will quickly realize that, and will tell others not to buy it under any circumstances. Even worse it could end up being malware, which also happens.
There are unscrupulous folks in these open stores who will abuse the system and tell others to buy the next “Mildly Upset Birds” app, which actually turns out to be a virus that's transmitting all your personal information from your phone. But that will quickly get caught and be pulled down.