What’s £200 million between friends?  Well, in this case, it’s the amount by which eMarketer believes it overestimated worldwide social networking ad spending in a not-too-distant year.

 eMarketer’s Social Networking Figures
(Photo Credit: eMarketer)

So much for the idea that 2011 would see £2.4 billion spent on ads; eMarketer now says only £2.2 billion will be contributed.  "Social network sites are still trying to figure out what sort of advertising works," states Debra Aho Williamson, a senior analyst specializing in social networking. "Tapping into consumers’ conversations and spreading brand awareness virally has proven more challenging than companies originally thought."

Granted, given that so-called economic experts can’t even agree whether or not the U.S. is in a recession, a lot could happen during the next three years.  eMarketer emphasized that social network ad spending still has a leg up on overall online ad spending, too.

This development doesn’t look encouraging, though, given that traffic to Facebook and MySpace fell between March and April.  Then there’s the matter of the $100 million Facebook recently raised.

By the way, the amounts of £2.4 billion, £2.2 billion, and £200 million convert to about $4.7 billion, $4.3 billion, and $390 million, respectively, but we wouldn’t want to wager on what the exchange rate will look like down the road.