To me that sounds like a value judgement based on a positive belief in a potential customer being as efficient at determining the "relevance" of a particular advertisement - not something that I find common with most potential buyers.
I believe a case can be made that if an informed consumer is searching the web for information relevant to a product they are interested in (in my mind the 'ultimate' impression to get your AdWord in front of), they are exponentially less likely to click on a "sponsored link", no matter how unobtrusive, relevant, or appealing, than they are to scroll through the search results until they find - for example - a relevant forum thread with posts by owners of the product in question, or a review that's relevant to the product in question and perhaps offered by a recognized and trusted source.
That, though, I believe is a small (but growing) subset of those who are likely inclined to purchase something even -remotely- related to what they are searching for. And that subset is an even smaller percentage of the people searching Google, who want example configuration files for Linux mail server daemons or shipping and handling rates for a particular international carrier. Neither of these two are likely to click an ad hawking Linux configuration bibles or packing materials, no matter how relevant the ad.
Someone may need the information in that book, or may need the packing materials because they need to ship something from England to Arkansas, but that doesn't matter one bit. What matters is they are searching Google because they want a particular, tangible bit of information at the speed Google has always delivered it - instantly.
Google succeeds as a search engine because users are exposed to the least amount of hassle between them and the information they want off of the Internet. Those are the people that relevancy matters to - people like me - "give me the most relevant page for 'adwords forum'" was what I told Google. I got two answers back:
A) Here's Webmaster World's 'Marketing World' section, specifically on Google Adwords, with some text we spotted the last time we visited it.
B) Here's an advertisement for beating the AdWords system, you can reach 100 million people instantly and make 100 zillion dollars in 5 minutes while sleeping!
(I paraphrase, nearly as inane though)
If I'm interested in an AdWords community, it stands to reason I may have some questions about it. Since it's an advertising system, it may well be that I'm interested in making money with it by advertising as effectively as possible, which the top product on the search certainly seems to offer. Thus, was I presented a relevant advertisement that there's some legitimate expectation I might click on? Try it, and you'll see what I mean. Looking for the phone number to the movie theatre downtown? Get 21 DVDs for $0.01! Looking for your credit card company's website so you can start managing your account online? Repair Your Credit Instantly!
I don't necessarily think Google's algorithm for determining the relevance of these links is wrong, since they are both topical. However, neither of those two example searchers are going to click on those advertisements out of -relevance- but instead for the same reason I click on Internet advertisements - "hmm, interesting. Well, I'll check this out and track down that website/phone number in a minute, because this might be cool." And the further down the list you go, the less "topical" the AdWords advertisements become. That's not exactly my definition of "relevance", but again, I suppose it is "topical".
Try it yourself, with a - imagine you're a typical PC user who's just seen a breaking news story on CNN about how the latest Internet worm has ground traffic to a halt. You've got no AV protection, but you've determined to spend what it takes (within reason of course) to get the best stuff... so you go to the only search engine you ever use any more, and type in
"pc antivirus software comparison"
Like I say, try it and see what you get - [google.com...]
I'll tell you what I got on the first page:
> 1 Ad for a popular antivirus brand at $20 off retail
> 1 Keyword spam from a MAJOR Internet search engine
> 1 Page title "compare anti virus" that apparently allows you to compare the quality of 125x60 pixel ads offered to affiliates.
> 1 Price comparison search engine's results (which is almost close)
> 2 Enterprise-class software evaluation firms (TCO & ROI consultants it looks like)
> And what set of ads would be complete without the chance to get a major PC security suit absolutely FREE*
*You have to submit a credit card application
Now look at the second search result.. tell me what you think Joe Noantivirus is going to click on.
But I digress... let me put it differently.
If relevance was relevant to success in advertising, I would have been able to go to more than three websites in a row from 1998-2002 and not be offered the opportunity to "Punch The Monkey And Win $20". That would have died, instead of spawning in to "Smash The Fly And Win A Free iPod!".
I was outside working on my car last weekend when my friend called me in and asked me if he could "put my email [address] into this web thing" because it turned out he actually had to hit the fly AND sign up 8 friends for the free iPod.
Oddly, he left shortly after that ;)