so, 'dumb' but not 'invalid'... There might very well be networks (say not on the internet) where as-paths longer than 100 might be required. Saying: "they are invalid" isn't correct. Saying: "The use of as-path longer than 100 on today's Internet isn't helpful" is correct, or so say you and atleast blaine.
All I can honestly say is that I never saw valid advertisements > 100 used on the Internet. I can not think of a good use in the Internet provider space for an AS that long but who knows what may happen in the future. The reason we set it to 100 was that we wanted to give plenty of room for growth; realizing we were not going to be perfect about predicting future needs. We could have set it lower but 100 was a nice round number <grin>. I stopped recording all advertisements a few months ago but I suspect we are still sub 50 and I am sure someone on this thread probably has that info at their finger tips. Since the bug itself revolved around an 8 bit variable it may even be safe to set things at 200. If you are in a core role and you set the limit at something like 254 you may have trouble prepending your AS as it could tip you over the edge (WRT the potential for triggering that specific bug). Regards and, I believe, congratulations Chris! Blaine P.S. Nothing in the above constitutes a recommendation to apply configurations to routers. Use your own judgement and track your BGP table for a few months before playing with these knobs.