Google Instant's previews show the +1 button, so I see no reason why Googlebot wouldn't too. I guess Google wait until window.onload fires instead of just timin

Google Instant's previews show the +1 button, so I see no reason why Googlebot wouldn't too. I guess Google wait until window.onload fires instead of just timing the server sending the 1 HTML file. Google could also use data from Google Toolbar users but I doubt they do. As the article says, even with a primed cache, the +1 code slows down page load. It also said the overhead can be 2 seconds. If you're aiming for fast then that could double your page load time. External assets are very likely to be calculated into a sites speed as they generally take up quite a bit of the page load time. Of course, no one knows how much of an effect page speed plays in Google's algorithms. My bet, however, is that adding +1 to a fast site could easily make it drop a few places in the SERPs. If your site is already quite slow then an extra 2 seconds may only be a few % slower.