On the other hand, you've disregarded the possibility of continuing to browse after doing three things (or stopping prior to three things). If browsing is an endless stream, then facebook has to be followed by one of the other two, which is the angle he was working from. Depends how you frame the question and what assumptions you make; it's ill-defined right now.

Edit: On another note, in his place I would have sanitized my own history; a screenshot showing redtube and tube8 in the "visited" style is tacky, to say the least.