In the proof-of-stake proposals, actually holding old balances, and actively helping to certify transactions when challenged to do so, is what earns you the right to 'mint' new ledger-extensions. (And if you don't, your future transaction fees go up.)

Not sure all the kinks are worked out, but competing based on who best enables the fastest, most consistent, most-fraud-resistant global log seems to more directly benefit the community, than proving who's burned the most resources on electricity and specialized hardware.