Whilst it may technically be "iTunes et al"'s fault, you can't blame them. HMV had the chance to save the business but didn't do the right things. The prices are high, the staff are obnoxious and the business acumen? non-existent. HMV failed because it sucked. No other reason. But how long until we're told it failed due to piracy and the internet?
To be fair that is the truth. HMV has been overpriced since the days that Virgin Megastore was it's only real competition, yet it performed pretty well then. Maybe, maybe, it could have competed against the internet alone, but with piracy evolving at such a rate it had absolutely no chance.