Also, from the photo's it is only clear that he has the guys email address, and even if he did have his password I'm not sure what he could do with it without committing a fairly serious offense.
I really have no idea how you would go about contacting this person without putting yourself in a compromised position. I realize that you do not want people to jump to conclusions as to this guys guilt, however, at the very least he would be a leading suspect in the theft of this laptop, and that is not the sort of person I'd meet for a coffee and to talk about him maybe giving back my laptop.
Also, if you emailed the guy and politely asked him to return the laptop how long do you think it would take for him to get rid of it on craigslist or ebay?
Therefore, attempting to get more information on who this person is in order to build evidence that the police might be interested in looking at seems quite reasonable.
This same location method is used by iPads and iPod Touches, which also don't usually have any better way of locating themselves. The WiFi technique is even used for iPhones, in the rare event that they can't use GPS or cell tower triangulation at a given point in time.
As I acknowledged elsewhere, this is an excellent point, thank you.
I think making all reasonable attempts, including creating a webpage, to identify that person is well within his rights.
Ah, now this is another matter. It looks like the author of this blog has this other person's GPS location and Google credentials. I am not an expert, but I am also not sure that publishing these pictures in this context is solely a question of identifying the person.
So even if he is careful to avoid a blatant accusation, I still don't like the implication and I don't think that identification is the purpose. If it was, it would be easy enough to get in touch with this person without explaining what this has to do with a laptop.