WebmasterWorld moderator, martinibuster, started a thread named AdSense Ads with Phone # in Them. He asked if this is a good thing or bad thing to have the phone number in the ad copy in AdSense ads. Publishers only get paid based on ad impression or ad click, the clicks are what really bring in any significant money, I believe. So for the ad copy to contain a phone number and not require a click, the publisher does not make as much money.
Rodney in the thread breaks it out nicely:
Thinking about it as a customer: I don't think I would call a phone number just from seeing a few words of text before it. However, it would help that particular ad to stand out from ads that didn't have numbers as possibly a company that is more reliable with phone support if necessary.
Thinking about it as a merchant: seems like just another tactic to get your ad to stand out. I really doubt you'll get lots of calls just from the phone number and 3-4 words.
Thinking about it as a publisher: it seems like it would show that there are quality (ie: non-MFA) advertisers showing on my site, and if the merchant is correct, and the it makes the ad stand out, then that means that ad would get more clicks, which menas more money for me, more leads for the advertiser, more relevant ads for my site visitors.
But that is just his opinion.
Forum discussion at WebmasterWorld.