Come back soon!

The number of UK-based Facebook users fell five percent — from 8.9 million in December '07, to 8.5 million in January '08 — according to Nielsen Online.

This is the first recorded drop since July '06, when Nielsen began tracking data on the site.

The decline was speculatively attributed to the invasion of marketers, corporations and old people in what was previously the haunt of self-enamored college kids. Young people may be gravitating to niche networks that better align with their interests.

But Nielsen analyst Alex Burmaster asserts ongoing dramatic growth was simply never sustainable.

From last year to this one, the number of Facebook users has grown 712 percent.

"Just as one swallow doesn't make a summer, so one month of falling audiences doesn't spell the decline of Facebook or social networking," Burmaster consoled.