Well on the flip side, banks also wouldn't carry your money from A to B if they didn't get payed for it. So there's that.
And BC.I isn't in theory preventing this transaction from happening; it's actually encouraging it by trying to get it to a miner, which it's failing at for obvious reasons. On the other hand, wallets are preventing you from double spending the transaction because BC.I appears to be persistent on relaying a doomed transaction, so in practice, it is preventing you from moving the funds - even if through another transaction, indirectly.
Rest assured all these 'irrelevant usability issues', as myself and many developers would call them, will be worked out before long.
Thanks for your thoughts on this matter. Makes perfect sense, all the way around.
And
great news!! My unconfirmed transaction finally "fell off" of Blockchain.info, and I got my coins returned to me!

Only took 4 days!

Next time, try writing to blockchain.info support, and see if they can help. They're the retarded ones that still showed the tx, and everyone looks at blockchain.info, all clients do -.-