What do t-shirts have to do with story point estimating you ask? Plenty!
Working with organizations transitioning to agile I often find that estimating is one of the first areas of discomfort, and story point estimating is just too hard to grok for most. After all, most developers have been giving estimates based on time for most of their careers, and we come along and ask them to think of relative points for estimating. It often goes over like a lead balloon.