I have "thought" I recognized a handful of women online, doing a double take and maybe a bit of closer examination. Most of the time the evidence is inconclusive due to finding only a single pic, and in those the photo captures a partial profile or is of less than ideal resolution. Unfortunately am unble to identify very many women by their boobs or ass or other bits alone...
Other times have eventually come across other pics of the same or similar series and in those have decide alas, no, not the person I thought it might have been. Damn!