That's the power of more-or-less mandatory. Snapped by TheSixthAxis during the Vita Slim reveal event, Sony UK boss Fergal Gara presents a graph demonstrating how PlayStation Plus subscriptions have tripled since the launch of the PlayStation 4, which requires the service for most online play. (via The Escapist)
I would totally be disappointed about the PS+ requirement for online multiplayer, if Sony hadn't already convinced me to become a subscriber because they give away hundreds of dollars worth of free games every year.
Metro: Last Night (PS3) - $35 at Gamestop
Payday 2 (PS3) - $28 at Gamestop
Remember Me (PS3) - $35 at Gamestop
Street Fighter X Tekken (Vita) - $25 at Gamestop
Modnation Racers (Vita) $13 at Gamestop