The effectiveness of Skype ads

"Skype's homepage ad units are now a year old, and its conversation ad unit (see graphic) arrived five months ago to more groans than excitement. Forbes' TJ McCue described them as a "non-starter," lacking the targeting ability that parent company Microsoft offered with its Bing ad units.
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The telecom ran a campaign promoting deals on Nokia, HTC, Sony, and Samsung phones, using Skype homepage and conversation ads. Skype claims those ads generated a 29% increase in site visits in the first two weeks of the campaign.
Skype worked with comScore to recruit Skype users. Respondents were divided into two groups of over 300 users each, one a control group (did not see campaign) and test group (opportunity to be exposed to campaign on Skype). Both groups answered an online questionnaire to measure their awareness, opinions, and engagement with the brand, and comScore tracked the behavior of exposed panelists for four weeks after their first exposure.
Among other findings by comScore:
Key metrics like message recall, intent to recommend, and intent to purchase rose nearly 50% among those exposed to the conversation ads, and the lift was nearly 40% for the homepage ads.
Overall Brand Opinion saw lifts of 37% and 46% from homepage and conversation ads respectively.
Compared to the control group, comScore measured a 60% lift in brand message recall for those who saw the homepage ads."

Source:  Marketing Vox, 20th November 2012