Responses
Haha while the yaoi tag could be the obvious indicator, I think there's also the often-occurring human error of mislabeling something or leaving out info/details. (for instance, I read a shounen-ai that wasn't [also] labeled as yaoi, and yet there were explicit sex scenes in it. I've also witnessed Hentai scenes occur in the Yaoi-genre w/o being identified)
Everyones like DAMN, It'S A GUY I SWEAR, and I'm like THO; YOU DON'T NEED TO BE SHERLOCK HOLMES TO NOTICE THAT KAY?! (we forget about the damn abvious Yaoi tag now kay tho)