ESEA the e-sports community was found to have placed a btc miner in their client. Long story short an OpenCL miner was buried in the ESEA client which netted them around 30 BTC after about two weeks. While it is an ingenious idea it was pretty dishonest and completely unnacceptable for a community like that. It's kinda incredible to think a paid service like this had the "brilliant" idea to include this and not think they would get caught. Supposedly they managed to cripple a few GPU's with this for the people who left their computer running 24x7 with this client.
https://www.networkworld.com/news/2013/050113-bitcoin-hijacking-269312.html