“DESPITE the many treasures posted online, sports fans still can’t find videos of the first Yankee game they saw with their fathers, or download all of Pete Maravich’s behind-the-back passes.But Baron Davis’s recent demolition of the Dallas Mavericks is yours for the taking. The National Basketball Association said it would announce today a new video download store that it quietly rolled out at the start of the playoffs, allowing fans to download, for $3 apiece, playoff games from this season and last.”