Here is how the current starting NFL QBs were acquired:
1st round draft picks: 18 (E. Manning, P. Manning, Brees, Bradford, Cutler, Campbell, Flacco, Freeman, McNabb, Palmer, Roethlisberger, Rodgers, Sanchez, A. Smith, Stafford, Young, Rivers, Ryan)
2nd round picks: 3 (Favre-#33 overall, Kolb-#36 and Henne-#57)
3rd rounders: 2 (Edwards, Schaub)
4th round: 2 (Garrard, Orton)
6th round: 3 (Brady, Hasselbeck, D. Anderson)
7th round: 1 (Cassel)
Undrafted: 3 (Delhomme, Romo, Moore)
While there is a significant number of 1st round QBs that don't make it, over half are first rounders and Favre and Kolb went really early in the 2nd. Only 4 non-1st or 2nd rounders have had any sustained success (Brady, Romo, Delhomme an Hasselbeck).
I find it interesting that there's more success finding QBs in the 6th and 7th round or undrafted FAs than getting one in the middle (3-5) rounds.
What's the takeaway from all of this: a team's best chance at landing a franchise QB is finding the right one in the first round. Odds are the Bills will be looking to get one in the first round of the '11 draft.