Remember all of those stories about Google passing symbolic share price milestones such as $600 and $700? At its peak in November, Google was trading at $747.27/share, carrying a market value of more than $234 billion.

How times have changed. Three months later, Google sits around $450/share, and has lost nearly $100 billion in market value. Today, shares are down another 7%, on word from comScore that the amount of Google ads that users are clicking fell 7% from December to January.

In addition to the decline in paid clicks, I’ve heard several arguments both on the financial news networks and on various blogs as to why Google is tanking. For one, there’s the idea that as the economy cools, people are going to be spending less, and hence, clicking fewer ads. There’s also the lingering concern that Google has lost focus, expanding into areas like mobile and trans-pacific cable (there’s also the somewhat hypocritical argument that Google has no real revenue streams other than paid clicks).

Personally, I’d also argue that the quality of ads has gone down through the years, as complex search marketing and affiliate programs buy an increasing amount of space in search results, hence making it harder to find the best places to shop. In the past, I’d often find the ads more valuable than the search results for certain queries; this has definitely not been the case in the last year or two, at least in my experience.

Now it’s your turn to be the analyst. Today’s poll: