when your ex is a coworker -- and a silly one

A reader writes:

I work for a big technology company. We are the market leaders in what we do, and we are looking at doing more cool stuff everyday. And I work for HR in the global headquarters.

I have a 'frenemy' here. We used to date - our company is ok with employees dating and many employees are married to each other - and he treated me pretty badly. I am with a great guy now, but I still hang out with my ex socially.

Me and my ex are from two different cultures, and I am four years elder to him- I am in my middle 20s ( and no, he is not under 20 years ). We have not told our colleagues that we were dating, or that we broke it off.

My ex has posted his almost naked pictures online, posted drunk updates in various social networking platforms detailing his sexual exploits and his level of sexual frustrations, etc. He has even posted on public forums that he is going to apply for a job with a few competitors and has publicly disparaged our products in the past.

My question? To what extent can and should I be concerned? Personally, I would not hire a guy who is like this ( but that is my opinion). But I want to keep my comments professional. I am not sure that many people know that he talks that way about our products online. And yes, he proclaims that he works for us in his social networking profiles. I am yet to see him use our internal feedback and discussion channels to air his concerns about our products and services though.

My dilemma is this - I know more about how he is because of my past and current proximity to him. I have been with the company for around four years and do have a good HR network. I am not sure if I have to tell people who think of hiring him that he exhibits such behavior online. Many of my senior colleagues are not very well versed in social media and are not aware of all this happening in front of a large and varied public audience.

Should I mention that this guy is behaving in this way when someone mentions to me that they are planning to hire him? Or should I keep quiet? I want to be professional, and don't want my behavior to be any way affected by my personal equation with this guy.

Why not talk to your ex and tell him directly that this is the kind of thing that could hurt him professionally? You're in HR so you've probably got some stories of how you've seen this hurt candidates or employees; if he's skeptical, use those stories to clue him in. Tell him that you're worried that it's only a matter of time until this ends up hurting him.

In particular, tell him bluntly that if others in your company see him disparaging the company's products, chances are very good he could end up fired.

(What is up with this guy's judgment?)

Of course, a second option is to ask yourself how you'd handle this if it were any other employee, and then do that. And you could argue that your company is entitled to know that this guy is behaving like an ass. But he's your friend, and it sounds like you have the info that you have specifically because of that friendship and might not have it otherwise, so why not give him a chance to clean it up?

However, if you feel like you're in an awkward situation because you feel you have an obligation to share the info, a middle ground would be to tell him that this is the sort of thing that your job could obligate you to share, and that it's putting you in an awkward position, but that you want to give him a chance to clean it up before it comes to that. Then leave it in his hands and see if he pulls it together or not.

What do others think?