Let me speak from experience.
I had a very good friend of 10 yrs. I've always treated him as a
very close friend, almost a soul-mate but I have no special
feelings for him nor was he treated as a substitute.
He treated me as a very good friend too, but to him I became more
than a friend. On his 22nd birthday, I brought my new bf along and
he was heart-broken because he thought he had a chance since I
broke up with my ex. We stopped talking for a while but he
contacted me again when he pulled himself together so to me, it was
hey we are good friends again.
However, as some already know, we are no longer friends anymore and
he has been avoiding me like a plague since I got married. Never
once have I lead him on and I have always made things clear to him.
Never once did he say to me,"I like you more than a friend" other
than his 22nd birthday. Never once have we done or even have any
physical contact beyond what is considered more than a
friend.
I've always believed that a girl and a guy can just be very good
friends but since this incident I have changed my mind.