Also take in to consideration Facebook is trying to get companies to spend a lot on advertising their Facebook pages.
One way for Facebook to do this is prevent users from making "irrelevant or inappropriate" on the advertiser's page.
I have never seen a message like this before, but I rarely post comments on Facebook. I have, however, had issues with business associates spamming me. I found out firsthand just how difficult it was to unjoin a group. I also noticed that I could flag a comment as spam, it disappears, and then magically re-appears again later. These "spammers" still have their accounts.
Facebook is basically a controlled platform for spamming. Its for attractive girls to spam photographs of themselves to hundreds or thousands of males. Its for companies to blast out their messages to millions of people. There is little question that Zynga's initial growth came from saturating player's friends feeds with notices about their farm. All supported by Facebook's aggressive opt-in by default email notifications. If that isn't spam, I don't know what is.
Facebook's business model is one of figuring out how to monetize all of this noise without scaring away its users. One way you do this by making spam more relevant. The other way is by ensuring "spammers" that want to be seen fork over sizable amounts of money. This is something anyone buying in to their IPO should think a lot about.
As negative as that sounds, I like Facebook a lot. I refuse to use Google+ or any other social network. Because of Facebook I've been able to keep in touch with a lot of people who I would have never seen or heard from again in my life.
That said, I've seen a disturbing trend in my Facebook friend's list of attractive females de-activating their accounts (attractive females make or break socially connected platforms.) There is too much noise for them. And you bet, if something is "irrelevant or inappropriate" they will be the first to leave.