At the biggest bike shop in the area (this being Dallas area), I've been in there and been totally ignored, and have been in there and had 7 or 8 people ask me if they could help me. I think what makes the difference is how busy I am.

At the smaller shop two miles from my house, they nearly always have time to say hello and ask if there's anything I need.

There have been posts in the Clydesdale forums about large people being ignored. Some stores see a large person and think, 'That person's too fat to ride." Other stores see a larger person and think "That person's too fat. He/she should be riding a bicycle." But to carry it further, some stores seem more geared to high-performance biking, and and just assume anyone that doesn't fit that mold isn't a potential customer.