Essentially, that list is just facebook's way of making it more convenient for you to continually interact with the people you usually do, without having people you dont interact with show up in that list.
Some people are under the impression that the "top friends" that display on your profile/timeline are the people who have viewed your profile, but this is not true. In fact, the opposite is actually true. Think of them like "suggested interaction" in the way that facebook has noticed that you might want to interact with that friend again soon.
Now... what does this actually mean? I'll attempt to explain it in general terms... think of it like this...
Things that count as "interaction"
• If YOU keep viewing/stalking THEIR profile
• If YOU keep using search to look them up
• If you and another person are friends both using the same app
• If someone sends you a private message
• If you send someone a private message
• If someone posts on your wall
• If you post on someone's wall
• If someone likes something on your profile or photos
• If you like something on someone's profile or photos
• If someone comments on something on your profile or photos
• If you comment on something on someone's profile or photos
• If another person views your profile
• If you view another person's profile
As you can see, there are many ways to interact with someone else on facebook, and they all count towards who is displayed in your top friends.
Note the last two items in that list, and think about them. If someone comments on your profile, they have to go to your profile in the first place in order to add the comment, so in effect, they are viewing your profile, but not everyone on that list has viewed your profile.