David Sacks is having a big birthday party this weekend. You might call it “redonkulous.” I know, because I’m going and I have an 18th century costume on a hanger at home to prove it.

Unfortunately, I’ve already agreed that everything I see or hear there is strictly off the record, so that’s the last you’ll hear from me about it. I assume the existence of the party is fair game. If not, I may be sitting at home in an 18th century costume this weekend. [UPDATE: At the airport, holding said costume I got a terse email from Sacks uninviting me, because of the contents of this post. On a personal level, I regret that he felt he needed to do that, but on a professional level, I can’t self-censor what I write based on personal relationships, and I felt I had to disclose the personal relationship on a post about how much I love the product.]

At any rate, this sucks because according to a Tweet Owen Thomas read by someone sitting in The Creamery — a coffee shop near Yammer’s HQ — Yammer might be selling to Microsoft.

I’ve been calling around and received a lot of hang ups and vague answers, which doesn’t necessarily mean much. What little I’m hearing is that there are well-heard rumors of talks, but nothing is done yet. And these deals are never done before they are done.

My sense is also that there are some grade-A morons working at Yammer either way. Every reporter does meetings in The Creamery! It is gossip central. The only thing more boneheaded would have been a failed DM on Twitter saying “Hey, person sitting next to me at Yammer, did you hear we’re getting bought by Microsoft? Don’t tell the press! Ka-Ching!”

If my sense is correct, and it’s not done, let me plead (in futility) with Sacks as a Yammer power user: Don’t sell to Microsoft. Let’s just celebrate your birthday and nothing else this weekend, okay?

Aside from Twitter and WordPress, Yammer is the most mission critical piece of software we use to run PandoDaily. I’m a huge believer in the value of newsrooms. Gallows humor, asking each other for sources, or “Hey! Did you hear this?” or “Who has a better headline for that?” — all of that shapes great stories. And because so much of our staff is geographically spread out, Yammer is the only way we get that feeling.

On a typical day, a good portion of the staff is inside Yammer from as early as 7 am EST to the wee hours of the morning PST. If you’re awake, you are always connected to it. Someone recently suggested I archive the feed as a diary of the first five months of the company, and it’s not a bad idea. I heard that our executive chairman Andrew Anker recently told a mutual friend the best thing about being involved with PandoDaily was being on the internal Yammer feed.

I love it, because it’s easy, and it works. It does one thing very well. But here’s the thing: Yammer is still buggy. It needs more innovation. It has only scratched the surface of what it could be. And there’s increasing competition. At both TechCrunch and PandoDaily, people have pleaded to switch to HipChat. I’d consider it if Yammer sells, but I probably wouldn’t otherwise.

Beyond that, all of the hot cloud, collaboration companies are coming into collision with each other, albeit slowly and from other angles. Atlassian is coming at collaboration from the software developers, Chatter has a foothold with sales forces, Asana is in there too in the form of task management. Box could easily wedge into this space since it’s already a place to go when people need to share documents and files. Sharing and collaboration are kissing cousins in the software world. And don’t forget Jive.

This space is still rapidly expanding, changing, and innovating. And if Yammer sells to Microsoft, it’ll take itself out of the game. We’d likely try out some other options, because I just have no confidence Microsoft would actually give the product the support it needs. Because Microsoft understands social even less than Google does.

I’m not one usually of those people who says “Oh, I’m quitting, because you sold!” like the handful who protested when Instagram sold to Facebook (and then likely signed back up again.) For one thing, I have a lot more confidence in Facebook as an acquirer. For another, Instagram isn’t mission critical to my day. I can wait for Facebook to actually screw it up before quitting. But an application I run my business inside of is another matter.

Did I stop using Skype once it sold to Microsoft? Nope. Because Skype is baked. Even Microsoft can’t ruin it. And there is no real competitor to Skype, so I don’t have much of a choice.

Yammer isn’t in that position.

I should note, I don’t pay for Yammer, so there’s no real reason either party should care about my threat. Because the company hasn’t given me a great reason to. But we get enough value out of it, we would. Or we’d pay a better competitor if it was a reasonable price.