Mathew Ingram looks at what a downturn in online advertising could mean for small players, and even for Google:

This debate has been going on for almost a year now. Google’s stock price came under fire around the end of last year and the beginning of this year because of concern that the search giant might see a downturn in ad spending that would hit the bottom line. Has it? A little, but not a huge amount (although some say that could change). In fact, there are those who argue that search-related ad spending is likely to be the most durable even in a shaky economy — in part because businesses can get more bang from buying AdWords than a newspaper ad or TV spot.

I don't know. I rarely click on ads that come with searches. I'm sure some people do (else, why would the business exist at all?) - but I've pretty much always thought that most advertising is a pleasant fiction shared by the sellers and buyers: the sellers buyers pretend that the ads have value, and the sellers happily collect money based on that assumption. What would happen if that assumption were ever really examined?