No, I haven't ignored it, but you really should understand that no one - no one - can unilaterally impose a contract on another! The part you highlight says two things. First - that the information in the email is confidential and should not be forwarded. That is, legally, just a request. There is no obligation on my part to honor it. There is no consideration for complying - that is, since I did not ask for the email, had not yet agreed to its terms, and had not taken anything I wanted in return for it, its terms were in no way binding on me.
(Imagine the fun we could have if we could impose one-sided contracts on each other just by sending an email! I could write you: You owe me a million dollars -- and you would!)
Second, it says that the software and information about it is subject to the terms of the Customer Seed and Confidentiality Agreement. That is precisely the agreement that none of us in this discussion signed - because we could not. That agreement could well have been binding as it was bilateral - we would agree to Apple's confidentiality terms, and, as consideration for that promise, Apple would send us the beta form of the new OS. We would each get something, and so a legitimate contract would be formed.
I would also like to point out that 1) in this discussion we did not discuss the software or any information about it; and 2) by quoting the email, you discussed the same things we did, and if, by chance, you HAVE accepted the invitation, signed the agreement, and downloaded a build, you may now be in violation of a contract you actually have with Apple. I don't think so, since, in my opinion, you still have not discussed the seed or given information about it, but you seem to hold a different view on that point.
As for getting attention with protest - not really. I rejected the invitation to preview Mountain Lion, and would now do the same with Mavericks, as I need my only computer for work. For a day or two, enthusiasm got the best of me, and I'm glad it didn't work out. I only had to keep responding here because some people seem genuinely worried about their broken invitation, and it seemed that others had stepped in to try to bully them out of talking about it.