Shares of Google (NSDQ: GOOG) have been on a sustained decline since late last year, when they briefly hit the $700 mark. They’re now off about 35 percent from those highs, factoring in a decline today of more than 7 percent to $451.13 early this afternoon. The latest wave of fear seems to stem from a comScore (NSDQ: SCOR) report claiming a meaningful decline in click-through rates in January to 10.4 percent, from over 12 percent in the second half of 2007. Lehman’s Doug Anmuth, who queried various advertisers and search engine marketers, pegs the blame on consumers. Advertisers aren’t (yet?) pulling back from paid search, but searchers, perhaps because of the weakening economy, aren’t clicking on ads as much they have been. As TechTraderDaily notes, a number of analysts are piling on today, to varying degrees. Though between the share decline and the company’s mediocre quarterly performance reported in January, the market doesn’t need to be told that the bloom has started to come off the rose.