To be honest you can use any bitcoin gambling site or any exchange as wallet but it's not really smart thing to do. You don't have access to private keys, and one day you could wake up and see site is down, your bitcoins are gone and than you will come here to cry about your money.
Would you keep your paper money in other peoples wallet? I don't think so.
Very well said and a very nice comparison. Even on web wallets itself i dont any have trust on using and storing large amounts of bitcoin thats why i decided to always put most of my bitcoin on cold wallets because i do feel much safer in this state but entrusting my bitcoin on Freebit.co would not be possible and i would rather choose up blockchain than on this one and i dont care if theres interest on storing it,doesnt matter at all.