I know plenty of straight guys who have made out, usually on a night out when everyone's had plenty of drink and stop caring about what society tells you is appropriate...will get down from my soapbox now. But seriously, I knew guys at school who would dare each other to kiss - and my Portuguese friend told me that loads of straight guys used to kiss at parties and nights out when he was at school. Maybe this is just the difference between Europe and the US though, I dunno...