On the fourth day of the federal government’s ebook pricing trial against Apple (s AAPL), Amazon (s AMZN) and Google (s GOOG) executives offered testimony in hearings that were often fraught and occasionally funny — but still introduced little evidence that was new or surprising to anyone who has been following the trial.

Kindling on the fire

First up on Thursday was VP of Kindle Content Russ Grandinetti, whose testimony continued from the previous day and who was questioned by Apple (s AAPL) attorney Howard Heiss. Heiss sought to demonstrate that Amazon needed participation from all of the Big 6 publishers in order to launch the Kindle Store in 2007,; to make it clear that Amazon was aware of publishers’ dislike of the $9.99 price point long before Apple came on the scene; and to show that Amazon had reasons of its own to switch to agency pricing, beyond the…