Tim,I agree with you that the sheer amount of detail comprising the OTU is amazing. For myself, a big part of the draw of roleplaying is the discovery of game settings, and perhaps that's why some of my favorite RPG supplements have been setttings (Library Data A-M & N-Z, World of Greyhawk, etc). However, the existence of professionally published D&D worlds [Mystara, Oerth (greyhawk), Faerun (forgotten realms), Golarion, Eberron, etc.] hasn't prevented individual fantasy gamers from creating their own. Almost every GM worth his (or her) salt has at least taken a stab at doing so. So why should the existence of the OTU prevent Traveller players from doing likewise, not merely creating individual worlds to plop into the OTU, but starting fresh with top-down setting design? I can remember doing some of this back in the day (by which I mean the 1980s). It was fun, and I got to run a few campaigns in this alternate setting. But it seems to me that I was the only one doing this. Everybody else just gravitated to the OTU, and I'm not 100% sure why.
In any case, thanks for bringing up the question that allowed me to unload a bit of baggage on this topic. As for being brave, I think we've got a pretty polite list given that fact that I wasn't tarred and feathered. :-)