Andrew Koch crunches some numbers on the question: will Roger Clemens get beaned in the NL? His answers:

Does Roger Clemens hit more batters than the average pitcher? Nope. In 2003, the average AL pitcher hit 10 batters per 1,000 batters faced (BFP), while Clemens hit only 5.7 per 1,000 BFP. Maybe Clemens has mellowed in his old age -- he must have hit more batters earlier in his career, right? Right, but not that many more. Over his career, Clemens has hit about 8 batters per 1,000 BFP. He's really not that reckless.

Do NL pitchers hit fewer batters than their AL counterparts?
Eh... sorta. National League pitchers hit 9.6 batters per 1,000 BFP, slightly less than the AL's 10. That works out to about .72 HBP per AL game and .68 HBP per NL game, a marginal difference.

Do NL "head-hunters" get hit by a lot of pitches themselves?
Yes. Eighty-two National League pitchers made at least 10 starts in 2003, and they averaged about 9 HBP/1,000 BFP. The pitchers who hit more batters than expected ("Headhunters") were hit by pitches themselves once every 224 plate appearances, while the "more gentle" pitchers were only hit half as often (once every 487 PA).

The lesson learned: If you hit too many batters in the NL, expect to get thrown at yourself.

Of course, Clemens also throws at a lot he doesn't hit; the third finding is the most interesting . . . read the whole thing. (Link via Will Carroll).