I was going to mention the "virginity" thing too (I can't be the only one that thought that Sara maybe shouldn't have told Mia that), I also think he's not been that lucky with the ladies, or, more to the point, he's a little insecure with them (he had to have had those braces-including the headgear sometime near or in high school which probably didn't help--but call me crazy I I've always thought a guy with braces is adorable)..the look at who he flirts with, Catherine, Sara, Mia, Wendy..they are sort of the "unattainable" ones (but Wendy did sort of throw him for a loop when she told him to take her and her friend out for dinner) but anyway, he flirts with them because it's almost safe too, he wouldn't get hurt from any sort of rejection there...remember the stripper, she called him harmless..if anyone could read a man it would be her..and he is sweet, but that's my point, it lends itself to what I've always thought..Greg is a geek in hiding, he so tries to be cool, and granted I think he is, but I think even the other CSI's know it's just sort of a persona..he showed his hand a few times like with not knowing how to pronounce "Tupac" with that scene with Sara, and the whole "scuba diving" story in that scene with Nick..He's too adorable and the little bit of insecurity added to the BRAIN POWER that he has..it just makes him totally irresistible, well to me anyway, just that intelligence alone can be attractive, but throw in everything else--it's the total package.