men are just wired that way. u just have to look at them once and they think u like them. even if u were turning ur head to look at something else, and their face came in the way, they will think u were checking them out and want them. so sad.
Girls can act this way too, you know. A guy might just give a salam in passing and all of a sudden the girl's thinking wedding bells. Or if they think a guy is giving them unwanted attention, they say "what a creep" but inside they really like it (I know a girl who actually likes it when guys honk at her on the road).
It just depends on the person I guess. Some people need the attention.