I think saying that this list points out which cities have the highest LGBT population is somewhat misleading – as the population of LGBT folks, I believe, is pretty much consistent no matter where you are as a percentage.
This list identifies those who “identify” being LGBT. Or, out of the closet.
The list is not surprising to me, outside of maybe Salt Lake City. It is easier for gays and lesbians to be out and open in more progressive environments, places where they are accepted as-is.
San Francisco, Austin, Portland, Seattle and New Orleans certainly fit that bill. And in Utah, an ultra conservative state where the LDS church has a huge sway, they have just signed into a law a very unique law that gives the LGBT community equal rights protection in all aspects except for religious organizations and the Boy Scouts (which is mostly funded by religious organizations).
It’s really a measure of tolerance where coming out is the least stressful and lowest risk. I’ll venture a guess that half of the top 20 cities by population are just as much or more LGBT by percentage if everyone that was so came out. I mean really, places like L.A. (Hollywood), N.Y.C. (Broadway, TV), Miami, San Diego, etc.