Should move this to service/trading discussion imo, it's not really appropriate to put it in bitcoin discussion.

Anyways, pump and dump groups are extremely shady. The most popular one seems to be pumpmycoin, i believe. Their business model is to take in money from people wanting to become a member, and they give a list of coins that they probably already have held beforehand. People vote on the list, and the most popular one wins. Doesn't matter which one because they've got every single coin on the list already. They promise that they would pump the coin, but if you think about it logically YOU the investor is the one actually pumping, because you're buying in and naturally that drives price up.

So they're taking your membership money + making money off selling their already accumulated coins from the money their members invest. It's all a part of a very elaborate confidence trick.

See this youtube video, it explains everything in more detail: https://www.youtube.com/watch?v=2T-I9zZT8U8