It’s hard to knock Google for expanding their ad placement on their properties. After all, we are talking about their properties, properties that are free for us to use. But the problem, as we’re seeing today with its new ad box on Google Finance, is that users don’t like change — especially for the worse.

Google has added a large, square Google AdSense ad to the main page of Google Finance. Previously, this area contained financial news and stock information. Now it’s contextual advertising offering things like undervalued stock information, advice on whether you should buy Google stock now and tips from stock master Warren Buffett. Of course, all of this stuff is probably crap that’s not worth clicking on.

But people will, and so this move makes sense for Google to boost its ad income a bit. I just wonder what’s next? Ads on Google Calendar? IM ads on Google Talk? In the past, Google has said it doesn’t want to put ads on its front page, but when times get tough, a few extra billion dollars in ad money can look awfully tempting…

Update: Here’s Google’s official post on the matter. These ads on Google Finance are an expansion of the already deployed strategy for ad placement on Google Image Search and sponsored videos on YouTube. We should also be on the lookout for more prominent ad placements within Google Search itself for certain news items like “iPod,” the post says.

And of course we get the usual spiel about how these ads benefit both Google and its users:

Whenever we make changes like these, we carefully evaluate users’ reactions to ensure we’re holding true to our basic principles: that ads by Google should always be relevant and useful. Of course, these experiments benefit Google because they generate revenue from new sources — but by ensuring that we show the right ads at the right time to the right people, we’ll add value for users too.