Not saying any system is perfect, Lord knows none of them are. However, if I were a hacker who got banned, my first reaction would be to plead innocence to see if I could get lucky. As unfair as an unwarranted ban may be, you must admit that the guilty and the innocent will all sound the same in the aftermath.
That is why I don't get particularly riled when it takes awhile before they drop the ban-hammer. I figure the more time they spend narrowing down the suspects, the more accurate the end result will be.
P.S. I've been the "victim" of an unwarranted pfile wipe on BLOPS2. Max prestige, 80% of the extras unlocked...and reset to level 1. After some cross-examination of my 8 year-old son, he confessed to a a few matches of boosting head-shots to unlock camos (we've got 2 PS3s in the man-cave). Turns out I wasn't Activision's victim afterall!