I don't understand this common notion that if you don't like the way someone runs their business, you get to change their business model for them. Here's a quote from a pro-blocking blog post that nickb linked to in another comment:

"Frankly, as far as I'm concerned, if a webmaster runs a site that's popular enough that the costs become at all significant, the onus is on him (or her) to find ways to cash in on that popularity to keep the site going. The visitors have no duty at all, and they certainly aren't obliged to go out of their way to make money for somebody else."

My response is that they did come up with a way to monetize their content (ads), but you don't like it. Too bad. Don't go to the site if you don't like the way they've chosen to make money. This goes along the same lines that if music is too expensive, or has DRM, that you therefore get to download it for free via filesharing, bittorrent, etc.... You don't. You're only ethical option is to not buy the content. That's the only ethical way you send a message (in this trivial context, obviously if were talking about human rights, etc..., the ethics of protest methodologies become more complicated). If I think something in a brick and mortar store is too expensive, would anyone think it was ok for me to just steal it? I don't think so.

A lot of the complaints about bad advertising practices, obtrusive adds, DRM, overpriced content are in fact valid complaints. But, you don't get to overrule the content provider's methods just because you feel like it.