Facebook etiquette - refusing friend requests?

Background - I am in my mid 30's and I have just joined Facebook. I looked up a couple of old friends from my high school days and added them as friends. No problem. It has been great catching up with some old friends. Fast forward a few days. I am now being bombarded with requests from individuals from high school to add as a friend. I went to a relatively small school and these people have obviously found me through mutual "friends". The problem is that most of these people I barely knew in high school and I am dumbfounded that they would send me a friend request.

So, my question is: Is it considered rude to deny a friend request? My basic info and what I am doing these days is in my public profile, so any of these people can satisfy their curiosity just by looking at my profile. I have done the same for some old classmates, just to see what they look like these days and their family status, etc. Do we really need to be "friends"?

I would prefer feedback from others who are around my same age. Did you experience the same thing when you first joined? Have you been ignored by old "friends" and did you take offense to it, or is this it a common thing and you just move on?