So you support people taking your code, modifying it to skim bitcoins off the miner, and then releasing the binary without releasing the modified source code?
That's one obvious consequence of MIT licensing, and has been going on for decades. I doubt it is a surprise to satoshi, or anyone else.
Either MIT or GPL, both licenses are fine. MIT has been working great for *BSD and X11; there's no reason why MIT would be problematic for bitcoin. GPLv3 adds some helpful patent language, that's about it. Bitcoin's patent problems are in the area of linked libraries (openssl's EC-DSA), not with bitcoin itself, so that does not seem like a large concern here.
Speaking only for myself, as a programmer who has created or worked on dozens of GPL'd projects, including some of the largest in the world (kernel, gcc).