This doesn't sound right at all. I am not familiar with US agencies but I am sure many agencies are ok with knowing donor and the rights of the child to find out later? Some agencies will facilitate donations with donors who are fine with contact etc. This doesn't sound good to me at all - I would really question this agency about this. I don't personally think it is right for you to have to sign this. Have you checked out how reputable they are?
I think you will find opinions are biased - that is the nature of them.
I personally would not go for this at all as I believe strongly that the child should know as much as possible about their donor when and if they want to. I personally am in the tell camp - I would never lie to my child or be able to deprive them of their history and right to know how they came to be (and to find/meet their donor if they want). I realise this is a very personal opinion (I am doing DE)and will always generate controversy.
I would advise posting this on the Looking to be a Mom thru Egg Donation board to get some opinions on this from women who have already or who are doing egg donation. Yes they are biased but I believe those are exactly the people you should be talking too - people who have first hand experience of this NOT people who have never had to consider donor eggs. Perhaps you could also canvas opinion on the people who have actually had their children by DE as well?