Climbing in Skirts

In the midst of this dating frenzy I just wanted to take a moment to say THANK GOD I AM NOT OUT THERE. After a horrendous break up and a life changing move back home to Texas I am in a committed and purdy spectacular long term relationship with an actual man (as oppose to a guy or a boy) who is not only good looking, smart, funny and tall but who is interested in me, my life's hopes and dreams.. He's awesome and the last 9 months has flown by.
That being said.
I'm friends with most of my ex-boyfriends. Maybe I've mentioned it before here, if not, now you know. Many of my exes and I talk on almost a daily basis ok, like two exes on a daily basis many on a weekly/bimonthly basis.
My question, due to recent circumstances, is the age old "When Harry Met Sally" question: Can a man and a woman be friends? What if they've been intimate? Is hetero-friendship a step forward or a step backwards when it comes to intimacy?
Somewhere in month 5 I got an email from an Ex. We'll call him Jacob cause that's what he is called in my Nanowrimo piece. Jacob wanted to go to dinner with me and I had the sneaking suspicion that it was because he had broken up with his latest. (Cause well, that's what happens) I went anyway, cause well, we were friends at one point and I was up for a laugh.
We've since hung out quite a few times, and time before last he admitted that he was bummed that I had a boyfriend. I laughed. I laughed right in his face. I may have even slapped the table and leaned over in the booth but the point is--at this point should I stop hanging out with him or should I figure he'll get over me and find a different type of distraction girl? My wonderful boyfriend of course (after much deliberation) knows about this now and his first reaction "I feel bad for the guy, cause I know what its like to have the hots for you and well, it would be sad if nothing could be done about it."
His second reaction when he realized that we had previously been naked was a little less understanding but nothing a little communication and crying couldn't fix. I hung out with Jacob a couple more times, and laid down the law. Point blank stare with a super serious "I'm not interested, you can't win this. Give up." And he got the hint. We stopped hanging out so much but he checks in every once in a while.
Can men and women be friends? Sure, but only if boundaries are set. Oh and if the girl has a kick ass boyfriend, that's gravy.