If your friends request inbox is full of invites from unknown people and you want to stop them from sending you a friend request, there is a very simple way of doing that. Follow this tutorial to find out how to adjust your privacy settings and hide your profile from unknown people on Facebook.
To get started follow steps below:
Step 1: Go to Facebook.com and login into your profile.
Step 2: In top right corner of your screen click on down arrow and from drop down menu click on Privacy Settings.
Step 3: Under How You Connect click on Edit settings link.
Step 4: In window that opens up you should see three or four drop down menu. Use those menus to adjust the privacy level you desire for your profile. If you want to block unknown people from contacting you, you should not choose Everyone from drop down menu which will certainly keep spammers from your profile.
Step 5: Once you are done with adjustments click Done to save your changes.