David Marx at Néojaponisme has an informative lament up about the closing of HMV's Shibuya branch, complete with a run-down of the store's cultural significance. (Short version: it helped foster Shibuya-kei bands, including one or two I absolutely love.)
I never spent as much time or money at HMV as I have at tower, but I spent enough. And at Wave, which he also mentions; Wave in Roppongi was my first brush with Japanese music-store nirvana, so I always had a soft spot for that chain, too. ...I rather think HMV's financial problems might have been entirely due to me moving back to the States. Like Willie Dixon says, "I never said I was a millionaire - I said I spent more money than a millionaire."