Today's Velonews has an article by Leonard Zinn talking about the fit, safety and durabilty issues tall and large riders face and some of the steps he has taken to address there.  He points out that are real issues of safety and durability he is not in a position to address.  (Like drivetrains.) 

One of his customers replaces all of his wear parts every 12 months!  Basically stripping the frame and replacing everything.  (And he wiull only ride titanium.)

Good article.  Approaching must read for riders over 250 pounds. 

Ben