Well, I remember reading something like that once, so it must be true. ;)

In all seriousness, I did some Googling and the closest I can find is this:

"One final reason is that Satoshi was opposed to putting non-Bitcoin related data into the main chain. As creator of the system, his opinion should carry a lot of weight with anyone serious about extending it."

https://en.bitcoin.it/wiki/Alternative_chain

I realize that is close to being useless, but I can't find the direct post in question by Satoshi that it is referencing. I seem to recall it not being Satoshi, however, but one of the current devs that I read a similar sentiment from.

But again, I don't have any direct links. I apologize.

in the original thread, which I linked above, this possibility was discussed. however it would have meant tying bitcoin to a project which has a lot of uncertainty and is not the core use case. miners/stakeholders have to agree with (major) changes so it's up to them making decisions. so the devs are really very much constrained to the original design. how this will play out is not quite clear. advanced features (payment protocol) are pending for quite a while. technically the integration is easy to do. the namecoin source has very few original lines of code. it is rather a question of consensus I think. Mike Hearn discussed this here: https://medium.com/p/b64cf5912aa7 "It’s not a bad idea, but it’s not practical for our needs right now because it has no users. "

the NMC network has some serious hashing power, look it up

As I understand it, merged mining an altcoin is essentially free money, therefore as mining margins narrow miners will have to merge mine major alts in order to stay competitive.