Well this was an odd decision. Driver is still playing at a high level, but at age 32 he probably has more good seasons behind him then ahead. From the 2007 Pro Football Prospectus:
There is nothing horrible about the extension, but it seemed unnecessary. If he manages to hold off father time or injuries and remains a productive receiver into his late 30s, then it is unlikely that his last season will be 2010 anyway so it isn't like he was trying to sign his last contract. Since the NFL is now handing $32 million to WR Kevin Curtis maybe Driver was privately upset that he locked in at last season's prices and GM Ted Thompson was trying to make it up to him.