The system has been changed and now members can only have 100 outstanding friend requests. To keep friending, simply go to your outstanding requests, and retract some or all of them, and you can continue friending.
Hos to: Click "Friends" in the upper right of the page. When you click on the "Requests Sent" tab, you can withdraw them one at a time, or if you go to the bottom of this page, you can click "Withdraw all _____ requests".