I know what you mean. To us guys...and well, I guess I'll clarify what I said. I'm not encouraging that guys have relationships with really good girl friends; things just happen, and if they do, you shouldn't avoid it. But with that aside, I do think guys draw a line between girl friends and girlfriends, and try to keep that line intact.
Am I wrong? Because with one exception all my relationships have been with people I'd just met that year. It usually followed the pattern of meeting them, like a semester of random hanging out, and then a semester and summer of going out, and then breaking up. That was high school for me. XD