Why? I don't really view Bitcoin as currency and if someone makes a mistake sending coins it's just part of the game. Bitcoin is a get rich quick scheme that has gotten out of control. I'm sure wherever the real "Satoshi" is, he's sitting on a pile of coins and is slowly liquidating. He and anyone else who got in on the ground floor is making a fortune at the expense of more recent bitcoiners. If you look at the stats, the majority of coins are being held so there is always the possibility that everyone will cash out and the market will collapse. You can play the game if you like, just be aware of what's happening here. I just wish I had thought this whole thing up.
P.S. I do mine small scale for fun and I'm running a slight profit, if they really do ship out some reasonablly-priced ASICs I'll probably pick one up. I'm making a lot more money on my web design and programming business, something to think about.
You're trying to rationalize it. Whatever your views of Bitcoin, they don't morally justify taking the coins, and this is coming from someone who would take the coins, mix them, and hoard them like no tomorrow.