MtGox's HTTPS will prevent any MITM attack unless the attacker compromises a CA or something.
Just curious theymos, what is your take on what was going on with all the charts when it was cycling in a loop between 6 and 7? After about 25 minutes those cycles were erased and the market sat at 6 until orders that were placed during the swings on the charts were executed. Anything is possible and I have never seen anything like what happened today.
I will tell you exactly what happened today. Ready?
Actually, gox just uses a queue with timestamps. Their order matcher can fall behind during busy times.
When the queue is busy, everyone sees huge price swings and they try to place orders, but their orders are going to the queue, not the market. The swings you are seeing right now on mtgoxlive.com are at least several minutes old already, possibly much older, and everyone frantically clicking their trade buttons and the bots scrambling to make sense of things are just making it worse.
I gave a much longer answer to (more or less) this same question several months ago. Feel free to dig it out of my post history. And, just to repeat myself:
It must be hell to be alive today with no clue about how anything at all really works.