Ball security is definitely not one of his strengths. That number is pretty high because usually his fumbles come in bunches. He has fumbled twice in a game a grand total of 12 times in his career. The Falcons are 8-4 in games that Vick fumbles 2 or more times in, and 13-6 in games that he does not fumble in but manages to throw a minimum of 10 passes. Those winning percentages (66.7 vs. 68.4) are practically identical, so ball security really hasn't put the Falcons in a lot of positions to lose.
You should note that some other QBs also have ball security issues as well, looking at their last 50 or so games:
David Carr - 45 fumbles in 52 games = 0.87/gm.
Drew Bledsoe - 44 fumbles in 56 games = 0.79/gm.
Daunte Culpepper - 50 in 53 games = 0.94/gm.
Aaron Brooks - 41 in 57 games = 0.72/gm.
Vick's average is 0.82 a game, so at least you could say he could get worse.
It's interesting that in games where Vick fumbles "only" once, we post a 7-8-1 record, a losing one.
So in games where Vick puts the ball on the ground, pray for another one.