Hmm, I hardly ever see it. I may be visiting very different sites or using different "blockers" than you are. That bar is the newer version of an older message, but it's the same issue: there is an unresponsive script in the page which either (A) is going to spin its wheels forever and needs to be killed, or (B) needs an unusually long time to complete and just needs a little more time. I think getting rid of the option means some tabs will simply lock up with no recourse, but I don't know for sure, there might be some other way to kill a tab. What have you tried so far to resolve this issue?