Well not forever. Woodward and Bernstein knew who he was, and they had a deal that they could reveal Deep Throat's identity upon his death. I guess he decided that he was now too old and feeble to fear retaliation and wanted to see some of the media hoopla that he'd miss if he took the secret to his grave.
Anyway, it's cool. Dunno if it's as meaningful to you under-20 folks out there, but it's certainly a part of my life.