That's what I want to know - it's so confusing!!!!
When I was at high school it was so easy - the guy said 'will you go out with me', the girl said 'yes' and that was it!
Now, it seems to me (28 yrs old), that if a girl asks if it's exclusive a guy thinks they're getting heavy and runs a mile. If they don't, the guy thinks they have free rein to see/sleep with other people under the pretence 'I didn't realise it was exclusive'.
I know it doens't answer your question legend, but it's kind of what I was getting at with my qu in r+d so I'll keep a close eye on your answers.
In short - I don't know! Experience has told me to assume partners are seeing other people unless a conversation about exclusivity has taken place, which then makes me wary to sleep around.