How can Blockchain.info wallet send unconfirmed bitcoins? So i just opened a Blockchain.info wallet after years of using Bitcoin-qt. 

My Blockchain.info wallet had an empty wallet, i sent some bitcoins to it and right after that without waiting for confirmations i sent some bitcoins to satoshidice just to test. To my surprise the transaction went through, how is this possible if my bitcoins didn't even have 1 confirmation? 

If Blockchain.info "lends" me bitcoin, how can it do it?
No, it does not lend you bitcoins but rather it spends the very same TX outputs that you have sent there. Thus, if your transaction turns out to be surpassed by another one (double spend), then also the transaction spending its output will be considered invalid.

It's like cutting a branch on a tree: all sub-branches will go down with the root one.