Typically used in today's working environment - sudden responsibility syndrome (or SRS) is defined when a co-worker, usually a manager, deems that you are now responsible for work that was previously theirs to do.
Sometimes, the reasoning for delegating the work is legitimate, but it's often simply because the co-worker/manager is a lazy asswipe.
Manager: "Hey Ron, I'm gonna need you to take over the filing of the weekly error reports from now on, OK?"
Ron: "I guess, but I'm already working late most nights just trying to keep up with my regular workload. Did you just get some new contracts that are going to burden you or something?"
Manager: "Oh good Lord no...the boss wants to take me golfing on Wednesday mornings. Oh, that reminds me, I'll also need you to cover all of my phone calls and emails during that time as well"
Justin (to Ron): "Damn dude, looks like you just got a bad case of SRS"