Remember when Plaxo was relevant?.. Keeping the contacts up to date was a real problem.. Still is to some degree, but much less so now with LinkedIn and Facebook where the contact info is attached to real people and doesn't need to be maintained separately anymore.
The problem of relevancy faces any successful project or business as the problems shift, but the organizations and the thinking has already been built to solve a specific issue and the more successful the product was at solving that problem, the harder it is to detach from it going forward. However, detaching from the yesterday's problem is exactly what needs to be done in the modern world as the ground shifts all the time..
So what's my solution? If I was Plaxo, I would look at what other problems/opportunities exist around the address book.. It doesn't take long to notice that contact info (business card) exchange is one of the hot issues.. If I was Plaxo, I would look at acquiring Bump App or building equivalent functionality..
In Today's world it's Stay Relevant or Die..