meeeh... wrong answer . No.hashing.power if incentives <= 0
everyone is free to have it's own block-chain. I would definitely not mine 10% or less of my total hashing power for another block-chain if that percentage it's not equal in price with the main block-chain. Actually I'm free to mine namecoins if I want to support distributed DNS, which I do, but my incentives are low for the moment. Namecoin will have to make it's way like bitcoin did, slowly, gaining it's users trust and no free hash power. It has the same security as bitcoin, don't need to worry bout it being fragile. Just my opinion.
But you would not need to sacrifice your bitcoin hashing to do namecoin (or whatever blockchain) hashing. If you have 1GHash/s of hashing power, with merged mining you could mine bitcoins with 1Ghash and namecoins with 1Ghash. If you refuse to give some project a free ride "just because", even though there is no loss to you, that's your decision, and you are free to do it. I suspect you would be in a minority though.