Yeah this is something you can easily get by highlighting text, right clicking and clicking search Google when you really want to know something. Any other time it's going to be more of a hinderance than a help.
Although in saying that I don't mind the ebook highlight a word and get a definition as usually with an ebook you don't want to break the flow and venture back out onto the net, whereas while browsing the net this is perfectly normal.
That's a very good point on both counts. In some ways this duplicates existing functionality (although in our case, it is mostly a side effect of trying to provide our users with the same features they would be losing when Apture is shut down).
As you said, though, there is value in providing contextual information about a topic without breaking the flow of the page. If we could turn Highlight into a tool that captures that value really well, I think the effort would be worth our while.
Although in saying that I don't mind the ebook highlight a word and get a definition as usually with an ebook you don't want to break the flow and venture back out onto the net, whereas while browsing the net this is perfectly normal.