Sharing, sure. But you're not agreeing to a hold harmless or arbitration clause. On further reading, it seems that there isn't a blanket arbitration, Equifax has said they will only allow you to see whether your days was compromised if you enter into one. Gray, legally speaking, but who's gonna test that?
There already is a class action suit filed in Oregon against Equifax for this breach, on behalf of 142 million people. So it's being tested. The key to any legal issue is to simply move it to a more friendly court. Consumer rights are MUCH more protected in the 9th Circuit, while RI and DE courts think businesses can do no wrong, for example. "Trust" has been argued to be a commutative property, as well. You trust A, A trusts B, so therefore you trust B. So even if YOU don't personally sign their agreement, you can still be affected by it in disturbing ways.