Google announced more changes last week, related to the amount of advertising that appears "above the fold" on a web page.
Their "Distinguished Engineer" Matt Cutts, said "Rather than scrolling down the page past a slew of ads, users want to see content right away. So sites that don't have much content "above-the-fold" can be affected by this change. If you click on a website and the part of the website you see first either doesn't have a lot of visible content above-the-fold or dedicates a large fraction of the site's initial screen real estate to ads, that's not a very good user experience. Such sites may not rank as highly going forward."
He went on to clarify that this isn't about the number of advertisements, but rather about how much space they take up. For most real estate websites this may not be a big issue as they don't usually devote much space to external advertising, but there are some sites that have been affected that are widely used by agents. Matt Cutts published a list of these including Twitter, Facebook, YouTube, MySpace and LinkedIn. If these are going to figure less prominently in search results, there could well be a knock-on effect for their users.
As always, the message is that websites should be about good quality, informative content and should focus on what the visitor wants to know. As Google's Cutts says "Overall, our advice for publishers continues to be to focus on delivering the best possible user experience on your websites and not to focus on specific algorithm tweaks. This change is just one of the over 500 improvements we expect to roll out to search this year."