Registering somewhere is not free. Apart from the invested time and wasted memory brain cells for the password there is also the never ending stream of spam that is to be expected from then on.
Also I think physical addresses are sold for several dollars a piece? So signing up somewhere with my address is worth at least that amount.
Since I created an account for nytimes.com in 2007 (I needed access to the complete archive for a project and paid $7.95 for it) I received the amazing amount of two e-mails, one confirming my order and one confirming the cancellation of the subscription after the project was finished.
In the following years I was never again asked to pay for any article I wanted to read and I never again received an e-mail. I really wouldn’t worry about creating an account for nytimes.com.
Still, I don't know in advance if that is true. Also are you sure that you haven't received spam mail from other entities than NYT, who got your address from the NYT?
Personally I think it's shocking that YCombinator have put up a paywall to HN, this site should be free to read. (I'm using time and brain cells reading it, right?)
Also I think physical addresses are sold for several dollars a piece? So signing up somewhere with my address is worth at least that amount.