Microsoft has done the decent thing and proposed to Yahoo. More even than Google's presence at Davos, it marks the end of the teenage years for the search and internet advertising business - excitement, discovery, novelty and rivalry were all part of it. Dreams of a revolutionary and different future.

Google announced disappointing profits, dragged down by lower than expected growth in pay-per-click revenues (the right hand side of Google search results and Google ads on others' web pages).

Click fraud - the activity by which you cripple a competitor's pay-per-click advertising campaigns by automatically clicking on their advertisements and causing their budget constraints to bite - at Yahoo and Google has gone up from about 20% last year to 30% this year. Almost 1 in 3 paid-for clicks is non-genuine.

Finally, and maybe most fundamentally, search engine optimisation means that the Google left-hand side results are getting inevitably less meaningful (see Google's Attention Deficit Disorder).

So, just as there are moments when even in the youthful and promising we glimpse the patterns that their middle age will fix and harden, so today, in these four trends, we can guess at the mature search business: corporate, branded, consolidated, oligopolistic, fraudulent, and gradually emptied of meaning.

We will feel nostalgic for the revolutionary internet decade that symbolically passed today.