The number of differences between Facebook and Twitter may be greater than the number of similarities, but that doesn’t mean that the companies haven’t been watching each other.

Several years ago, of course, there were reports that Facebook and Twitter had held acquisition discussions, but those didn’t pan out, and Facebook, some suggested, went on to acquire FriendFeed in an attempt to out-Twitter Twitter.

Since that time, both have grown significantly on their own, separate paths. But that doesn’t mean that Facebook’s interest in what Twitter offers has waned if its new Subscribe button is any indication.

In the coming days, this new feature will roll out across Facebook, making it possible for Facebook users to do two things:

  • Hear from people, even if you’re not friends“.
  • Let people hear from you, even if you’re not friends“.

That, in a nutshell, is what Twitter does, something that hasn’t gone unnoticed in the blogosphere.

Unlike some of Facebook’s privacy features, the Subscribe button is an opt-in feature. To enable it, Facebook users will need to click an Allow Subscribers checkbox on their Subscriptions Page. At that point, new posts that are Public will be shown to subscribers.

Needless to say, this is an interesting, and potentially useful feature, depending on how you use Facebook. At the same time, it raises an important question: at what point does Facebook go too far?

You can’t be everything to everybody, but much of what Facebook is adding to its service makes it appear that’s what the company is trying to do.

And it doesn’t appear that will change anytime soon. Yesterday, The Financial Times reported that Facebook CEO Mark Zuckerberg is delaying the company’s anticipated 2012 IPO “in order to keep employees focused on product developments rather than a pay-out“.

Even if there’s more to the story than that, on the subject of product development, one still has to wonder if too many new features will eventually start to cause more harm than good.