You know the answer The idea of decentralization has it's advantages but also comes with many problems and shortcomings that are often overlooked. The main problem we had with going a decentralized way is that many of the ideas and future services we have planned are incompatible or overly complicated to implement in a perfectly decentralized matter. We wanted to keep it as simple as possible for the users even if it means that they don't have control over their private keys.

If you are concerned that we may eventually disappear with your money than that's ok and you can simply not use our service and be done with it. That being said it's not like we are coming out of nowhere. ypool exists for more than 1 1/2 years now with a very positive history so far, see the other posters above.