Well I was just at my borders a half an hour ago and was reading the latest issue of Star Trek magazine. In it their was a section about the Andorians and how they've changed through the years.
At the end they had a paragraph about the Andorians in STO. In it was a quote from a STO official stating that according to their database, Andorians are on the top of number of players playing as them. I personally think that's awesome because they are my favorite canon species in game (Besides the Horta )
I just thought this was an interesting fact to share to the forums.
From my experience, many people are uncomfortable with aliens or playing as things that look like aliens. I would predict that the most played species is Human, followed shortly after by Vulcans and Aliengens.
I've seen a couple Andoians here and there...not nearly as many Aliens though. Aliens tend to stand out though, since a lot of them are very different, they stand out. So while they may not be a majority, they end up looking like one. It's the same concept that causes people who think of a trailer park to picture the red neck from the news talking about the ternader what tore through bubba's house sum'm fierce.