Originally posted by RollingGeek
You *probably* aren't going to top me --- 6'6" and 330 lbs.
(going down......believe it or not...just slowly.....)
I bought a Giant (not named for size 
) Sedona DX and it has been fine for me. I am moving towards a road bike in fact, but I have not had any complaints with the Sedona.
I would recommend a comfort / hybrid bike for the beginner big dude - they have a more upright seated position that will be kinder on shoulders, hands etc for the beginner. They also come with fatter tires which if nothing else, give you a comfort level (psychological) that your weight is not balanced on two razor sharp tires. Furthermore, these bikes usually have suspension forks of some sort that will help dampen the shock of the road (which can be hefty when you are pressing down with a lot of weight).
For what it is worth, when I was looking at bikes, I emailed Trek with my size, and they never really blinked. I guess if you were going to get an all carbon bike, it may prove to be a problem 
If the addicition sets in, once he has built up the requisite muscles and is used to more of the impact/shock, etc., then he can look towards a road bike.
IMHO of course, but I think jumping right into an agressive road bike might not be the best way to go. Comfort/hybrids give you more options too - if you get a hybrid, it gives you more off roading capabilities in case he finds that he wants to try that out.
I am by no means a bike expert - but this is what I have found out through personal experience, talking to LBS and reading this board.
Ditto
__________________
Just Peddlin' Around