As a structure-lover, I used to be in the matched camp, but am slowly coming around to the mismatched. The main change was someone pointing out that by allowing friends to choose their own cups, they become more invested in the experience. While people may become nervous choosing a tea, especially if they don't know very much about teas, and sometimes it is more practical as a host to select the tea, there is no pressure with cups.
The big drawback seems to be that it can be disruptive in "themed" teas. If people are trying to do the whole zithers playing, tea hut type experience, or some Victorian finger sandwiches on the lawn type tea, the one friend with the "Who farted?" mug is likely to bring them back to reality.
