Having more friends increases the weight of your discoveries, reviews and comments on StumbleUpon.
Recently, the stumbleUdon requires to new members to have at least 5 mutual friends:
"...every new StumbleUpon account that is entered into the system must have a minimum of 10 mutual friends. Hopefully it will improve the quality of the stumbles even more"
This is the place to join and place your StumbleUpon member link (yourname.stumbleupon.com) and to add the already posted IDs to your friends.
Don't forget to check periodically your StumbleUpon member page and to add all your fans to your friend, to make the friends be "mutual".
