I do. I tend to double or triple click to highlight the word or paragraph I'm reading. It's more of a fidgety thing than the need to track what I'm reading.

Side note: Any website that uses a double click on a word to launch a webpage defining the word or a search of their website with that word is EVIL and needs to be wiped off the face of the internet permanently. New York Times, I'm looking at you. (Besides, on a Mac I can right click and choose Look Up in Dictionary or Search in Google)