Sure,

Darkcoin is based on PoW as well as PoS. In fact the first coin, IMHO, to do it right, for the first time in the entire crypto world.

 Masternodes are up with 1k deposits, to make them active. This "retires" DRK's out of circulation, though at any second, a Masternode owner can cash out, entirely at will, unlike other PoS concepts.

 But, the point is to have them up and running, the more the better. It guarantees the Darksend technology, and future development features, like running blockchains for light-weight wallets, and lots of interesting derivatives there from, for real life use issues, like merchants, as one obvious and immediate example. But more is on the way.

 Speculation appart, the Masternodes are payed 20% of all mined DRK's right now. 576 DRK per day divided by all active MN's, to be exact. This creates a positive feedback loop of price increase out of an incentive based service!! A brilliant one!!

First side effect is miners get less pay. So there is no incentive in updating to the latest Darkcoin protocol. Right now, with the "spork" solutionEvan devised, a soft fork is set right now, essentially "inviting" people to update, before the real fork. Many, supposedly, professional mining operations have not complied. 20% is a significant amount.

80%+ of the network is updated. This is a tremedous POP, ergo, proof-of-professionalism. As of now, I blatantly shout greed, to the rest.

 The more the Masternodes are payed, the more incentive there is to have them up, depositing 1000 DRKS, creating scarcity, increasing price dramatically. Around 18% of the entire DRK coin is already locked in MN's. That is something like 4,5 Millions dollars right now, at these ridiculously low prices.

 So to conclude, no one is forced to update and pay off 20% to the nodes. Soon they will, when the enforcement is set. I'm sure they'll be quick to update then.