A contract-based account that runs a script of delegating donated SteemPower to new users who post legitimate introductions (possibly induce greater rewards for tying to external accounts like Twitter or Facebook for the sake of viral marketing).
I would donate to that account.
Also-- the blocksize issue is an interesting one. Has anyone done the research to see when it would become TECHNICALLY prohibitive, versus financially prohibitive (which shouldn't be the case)? I would imagine the technical challenges would arise far sooner. But, I'm not a witness so I dunno nuffin :D