Arstechnica is another good example of membership. If you're a paying member, no ads. Otherwise, ads. Best of both worlds and you give your audience a choice in how to support you.
The obvious bit is this: You are circumventing their revenue model. If you like/want to support their content, this is not an ideal way to show that support. Either turn off the ad-blocker or pay for membership.
Honest, lateral question: Now that I think about it, will DRM prevent the use of ad-blockers on a majority of websites? Could this be a sweepingly major side-effect of DRMs?