I forget who it was now, but someone once blogged that they would only advertise on their site for things they would personally endorse, that means no viagara banners unless the guy can reliably jack up a car using his Johnson.
Way too many people (I'm estimating high 50% judging by the number of idiots online) simply throw the code from a copy and paste into their layout and forget about it. Many people that use advertisements on their own sites choose to block them, so they're not viewing what they're subjecting others into viewing. This just ends up with malicious scripts or spyware installing sites on the other end of a faux Windows error box GIF running rampant because nobody gives a crap about what's happening elsewhere so long as they don't see it.
But until the "this is my work, this is my content, this is my brand" ethos of wannabe entrepreneurs that think that online advertising is the definitive way to make money online as spewed by the "online marketing gurus" that are a penny per 12 dozen these days dies out we really have no other choice but to fight it. Of course you could always trump their lack of legal knowledge (throwing the DMCA into an unrelated matter like they do) and contest that unless the site specifically states otherwise placement of advertisements is a legally binding endorsement of the advertised products and/or services and acceptance by the site author is made by his/her attachment of their own written work. So long as they insist that advertisements and their "work" which is usually just copy and pasting from another block with a trackback, come as a single inseparable package then we pretty much have their nuts in a vice.
Fact remains that if we turned around and started pulling legal jargon out of our asses (with much better comprehension I might add) we'd come out on top, although I don't see this silliness going that far but I do see careless webmasters ending up with some nasty legal action based on what I said above. People placing advertisements on their site have made their grave, now to settle into it.