I'm pretty confused here. As far as I'm aware, PM has not threatened Interference at all over this. I'm sure they realize that they need to spend their time going after the real threats (torrent sites, basically). With that said, I would sort of understand if they went after every leak of the album, as it's their duty to protect the copyright. Surely they don't want to go after U2 fansites, but they do have a responsibility. Regardless though, I'm pretty it hasn't come to that.
I know for a fact that the vast majority of people here are going to buy the album, likely the day it comes out. Otherwise, I would have not taken any part in posting the album here. If anything, I looked at it as a way to help promote the album. Pretty much everyone has mentioned that because the album is so good, they'll be buying a number of copies on the very first day for friends. On some level, I'm sure U2/PM/Interscope/Universal realizes this, which is why, as far as I know, Interference has not been threatened. Honestly, the people that are actually pirating the album from this leak and have no intention of buying the album probably wouldn't anyway. I just don't see them losing any sales over this.
I'm very sorry to hear that some stores are already selling the album. That is going to have a much larger negative impact on first-week sales then the leak ever could (and as I said, I think that will actually have a positive impact). It's very important to report these places if you see them, and to NOT buy a copy yourself, no matter how tempting it may be.
At any rate, I wouldn't start sending hate mail to anyone involved with U2 just yet. I think they've handled the situation just fine thus far.