The pay-per-call industry has a number of folks that assumed far faster growth than what has realized to date. Pay-Per-Call Struggles to Prove Worth in Internet Ad Realm from E-Commerce Times looks at the latest in the space, how the companies that offer pay-per-call advertising are posturing and making deals with mobile search service providers to expand inventory.
Search users are also slow to adopt mobile search, although acceptance of mobile, especially with local mobile search for travelers, is probably a mere matter of time and excellent small screen device options. Pay-per-call advertising networks hooking up with mobile search providers makes a lot of sense, since the small screen device people will likely be holding will be a phone.