What is it about the Saturn ECM???

What is it about our computers that make it such a bitch to work with? I hear things about the computer being locked, it's not a removeable chip, and a few other things. Since I write computer software for a living I know the basics of software development and all that jazz, and hardware-wise I've been building/repairing for over a decade. I'm just real confused as to what the EXACT issue is. Do all aftermarket computer tuners use the stock fuel mapping in the computer, and ours is that bad? I mean, almost any chip can be removed if needed, it might not be real easy, and locks can be broken. Maybe someone can enlighten me in as technical of terms as needed for this one.