There are three methods to determine who looks at you the most, and these methods are all probabilistic rather than deterministic. The first method is to refresh your profile page and see which friends appear again and again on your profile. Typically, these are the people who look at your profile the most over a given time period.
The second method is to invite every one of your friends to an event. When you look at the three categories of people: 1) people who have accepted your invitation 2) people who are still waiting to reply, 3) people who have rejected your invitation, you can see the top 5 people who appear are the top 5 people in each category who look at your profile or pictures.
The third method is to type in the first letter of each character in the alphabet on the search bar. You will see that the first name which appears is either likely the last person you looked at, or if that is not the case, it was the last person who looked at you.
These three methods can be tested quite simply. Just talk to that person who has been looking at you again and again and you will probably find an unexpected reaction, positive or negative, it will be strong. You can also test this by sending someone an email and many times, before they even bother to reply to you, they will look at your profile and you will see their name pop up on the name bar as your last looker.
Finally, you can just set up a few accounts, or ask your friends to look at your profile to see if I'm accurate.
Even more scary, if you look at facebook's friend suggestions, more often than not those are people who you don't know who recently looked at your profile. If you see someone who does not share any mutual friends with you, then you better watch out, because you might have a stalker on your hands.
As of today, I believe you will find that I am correct. However, who knows how long it will be before someone on facebook reads this article and asks the managers to change these settings. However, given facebooks long history of furtively violating our privacy, how much can you really trust the Harvard Undergrads who cut each other's throats to get to the top (See facebook the movie)? Remember what brought down friendster? -- the window which showed you who last looked at your profile. ONce people know that you know they are stalking you, then the entire system collapses. But the difference between Friendster and Facebook is that Facebook is not so honest to tell you who the last people who looked at you were, but they do it none the less.