[Toro]

I don't know if they can harm your game but they aren't Poker. Poker is not poker without money at risk. When I first set up my account on Pokerstars I went to a play money table to get used to the software.

It was a no limit table and I folded my first few hands but noticed that almost everyone was seeing the flop. So I decided to try an experiment. It was my BB and the whole table limped in for the minimum. I had some bullshiit hand but it didn't matter, this was an experiment.

I raised all-in, my whole play money bank roll whatever it was. Then I watched in amusement as the whole table, one by one called my bet. So if you want to waste your time there, fine, but I wouldn't.

Edit: To improve your game without playing for money try the Wilson software that lets you play against computer players. They have live game and tournament. I have these and found them useful, but of course nothing can replace real life play to improve your game.