Authors are a little more inclined to be on here that other stars for publicity sake, however I wouldn't find it odd if any person that's walked the red carpet had a Gaia account. A little more likely than neopets, less likely than facebook.
Would not surprise me if a minor celebrity was on Gaia. I wouldn't be expecting to see someone like Neil Patrick Harris on here but a guitarist for a really popular local band in Austin City or the lead animator on one of the current popular shows out there maybe. If they had been here from the early years and gained some of that fame in the last ten years I could see them still coming on from time to time to talk music composing or drawing with some of the same people they interacted with in their early days.