That's the point, nothing stop them to just disappear with your BTC. Read the "TRUST NO ONE" thread, here in this world it is a very possible thing
If you don't like it, then don't use it. Just don't go around screaming scam because you are too afraid of everything.
I think ewallets will play an important role in bicoin's success, but they must prove themselves trustworthy. I know that you should store your wallet offilne with triple encryption using an encrypted volume which is inside a safe in a locked basement without windows. However, this approach isn't usable (yes, there is a world out there where people don't know what an hash is). An ewallet
could provide security + usability, just like a real bank does.