I work in the same office as an affiliate marketing company, so it's their job to be checking Google all day for their adverts, but over the last few days this has been happening a lot. You'd think that having 20 people on the same IP address passing the check that they'd stop doing it, but no, we're still getting this. You would have thought that Google would have sorted this out pretty quickly.
I share the same public IP as a search marketing firm and am ALL too familiar with this screen.
The best are the inter-office emails that get sent off from IT asking if anyone happens to be using programs that automate search research...
I used to get this pretty regularly when trying to access a cached version of a page.
I've gotten this only when I was using IE on a school computer.
I used to get this when I used a proxy.
They seriously need to improve this check. I've got a static DSL IP at home, and I get that screen way too often. I shouldn't have gotten it a single time, really.