I would agree with you on principle here that perhaps an MMO gamer does deserve some rights to their character or their in game items, but I think the intrinsic problem is that your stuff only exists on a database owned by someone else.
Let's say you worked hard on your character. You spent hours on the character creation screen giving him a unique look, you penned a riveting backstory for him, and you created unique looking items for him to wear. (Presuming this is even possible in your MMO of choice.)
So what happens when the MMO dev releases a crappy expansion that completely breaks the game? What happens when you just get bored? What happens when the MMO dev goes under and they pull the plug? You can't take that character (along with all of his money and items) and move him over to a new MMO. He's stuck on someone else's server. You can take your D&D Character sheet to another DM's table and maybe he'll allow you to play with that character in his game. You can't really do this with an MMO.
If you are lucky, the best you could do is sell your character to someone else on eBay (except in the case where the MMO dev pulls the plug, then you're completely SOL). It is likely that you won't be able to sell him for a large enough amount to cover the costs of your subscription fees, however.
It would be interesting to see an "Open Source" MMO engine that would allow character transfers between actual games, but I doubt we'd ever see a commercially successful one.