I think if two people, especially unattached people, really like each other as friends, at some point someone is likely to develop feelings. That's natural, IMO. Whether you act on the feelings or not is another matter, but I guarantee somebody (usually the dude) is at least thinking about it, and is usually willing to risk the friendship to take it to another level.
If either or both are otherwise involved with other people, then it makes it the "friendship" train roll easier.
*thinking back to the days on the yard when the motto was 'girl, if you want a friend, buy a dog.....'
