Samizdata - 3:18 am on Nov 17, 2010 (gmt 0)
I can see that the Google web preview is being returned a 200 response when requesting the images
That is because the Google Web Preview bot does not consult robots.txt and acts "like a browser".
It is actually a prefetcher bot that appears to work like this:
If a site appears in the SERPs and its robots.txt restricts Googlebot access to images, CSS etc then the Google Web Preview bot will - once the "preview" option is chosen for a particular SERP - prefetch all such pages in the listed SERPs (not just the one selected for previewing) and will also cache the results.
So seeing the bot in your logs does not necessarily mean that someone previewed your site.
sites with flash and other technologies that generate blank areas are no doubt going to suffer
There are many reports on Google's webmaster forum and elsewhere of missing images and stylesheets producing uninviting screenshots and blank areas.
Martinibuster's topic here is "how we can benefit from the previews".
The first step towards any benefit is ensuring a good-looking preview image.
For now, at least, cloaking to the prefetcher bot gives the best results here.
Black tinfoil hat required.