Are you clicking on the guests profile? If nothing is coming up then it's possible that the guest doesn't have any reviews. If it's someone who's been a user since 2012 and has no reviews, I'd find it odd that they've been on the site for such a long time with no reviews, especially if they referernce having stayed at various airbnbs in the past. Maybe no reviews in this case because the host preferred not to review rather then leave a bad one? Most likely that's not it, probably a fairly new user with no reviews.
I just looked at your profile, and I see both reviews of your listings, and reviews that you've written for previous guests.
I go a bit further once I have the reservation confirmation. I cyberstalk! I look up the name to see if there's anything wonky that comes up with a quick search. If I search and the first hit is a twitter feed with pictures of alcohol fueled partying, then I'll check in more often and do a random drop by to say hello (oh, I though you needed more towels, wait - are you having a party?) conversely if I find out that someone is a marathon runner I might mention that there's a good running track nearby. I expect and am prepared for guests to cyberstalk me too.