[itblarg]

Three seconds? Yikes. Will be interesting to see how this impacts big money PPC spenders...

[guyzero]

By definition it won't affect PPC spenders at all unless someone clicks on the ad. You can only buy CPM ads on the AdSense network.

[itblarg]

It has the potential to drastically alter search, which thus would drastically alter PPC. The likeliest negative outcome is the gradual disappearance of any traffic driven from long-tail search keywords.

[slowpoison]

It won't affect PPC (pay per click) spenders. It will only matter in terms of CPM (cost per impression).