If a guy is scrawny, it makes him look even scrawnier and its very unattractive. If a guy is big, it makes him look bigger. If a guy has an amazingly hot muscular body, he may possibly be able to pull it off but unless a guy has the body of a god, he most definitely should not wear a speedo. Even if he does have an amazing body, its still more attractive to just wear a normal swimsuit. Don't wear a speedo...
I guess whenever I have seen a guy in a speedo he was wearing it to be funny... I probably wouldn't mind if an older, attractive and of course, fit man were to wear one. Don't regular or tournament swimmer men wear them too? so it wouldn't be all that odd, for me at least ;)
I can't think of a situation outside of competitive swimming where a speedo would look at all normal. I worked at a pool in high school and we always laughed about the few guys that wore them. It was just so obvious that they really wanted everyone to see their package.
I don't understand why everyone thinks swimmers wear speedos to show off their bulge. Where did this come from. I have jammers and speedo briefs and the briefs ate much better for me since they don't restrict my leg movement the way jammers do cause I have huge muscular thighs for a man and need to the freedom of movement.