So we now know who wrote the bad code (Robin Seggelmann). And we have an idea of why it is needed: Why does TLS need an explicit heartbeat protocol?
We can also understand why the client supplies the length: Heartbleed: Why does the client supply the length of the message at all?
But who proposed the form of the ssl heartbeat? Could there be some nefarious input from the NSA in the hopes that someone would code it the wrong way and leave it vulnerable for easier snooping?
I've heard rumors that they added flaws to several encryption schemes (if I could quote which ones and where I would), could this be yet another way they introduced insecurity in their desire to have a copy of everything?
I know this sounds like I might be wearing a tinfoil hat, but given the lengths they have gone to since 9/11, this does not seem out of the realm of possible.