I think the price is high given the main reason for purchase is the traffic (which, as we all know, is never guaranteed when it comes from the search engines).
However, I did listen to the investor call and there are several reasons behind their thinking (some of which I can't recall).
The contract for who supplies advertisers is ending soon, meaning Idearc can do what they wish with the traffic (i.e. put up their advertisers).
The number of additional visitors will increase their coverage a fair amount (7.7 Million on top of 21 million is a fair chunk).
Sites with more coverage can demand more from regional and national advertisers (and local ones where thier traffic is good).
Other cost savings are eluded to. In addition, they seem to be able to do this without having to disrupt their spending/dividend plans, maybe they are expected to expand in this way.
From personal experience I can tell you that having plenty of visitors (in the UK rather than the US) isn't an instant guarantee of someone paying big bucks for you, there has to be some underlying reason why it was so attractive. On the other hand, some people pay too much because they over-value an asset. We'll find out if it's a good price when the next big deal goes down or when Idearc gets sold.