Most sites have a support code, and when asked to s4s, two sites swap codes and paste into bulletins so their friends can see the code, and hopefully they get added.
It's not just for "myspace nerds" or whatever. Some sites out there have actual meaning.
"Sure. Code's on the page. Supporting now."
Most commonly used between Myspace contest/layout.. ect sites.
You copy a sites "support code", enter it in a bulliten, and write the subject as "add this site!"
Used as a way to gain more friend requests.
on Myspace s4s means
Support for Support
Its pretty much advertising someone else but its done through bulletins. normally people do s4s for Layout sites, Bands etc.
on YouTube s4s means
Subscribe for Subscription
You subscribe to someone because they subscribed to you.
Band: "hey we really need more friends can you help us get more?"
Girl: "sure but only s4s"
Band: "ok cool we posted a bulletin telling all our friends to add you, please return the favor"
-1 min. later-
Girl: "awesome I posted a bulletin to all my friends telling them to add you!"
In return both users receive a benefit.
Guy1: "hey everyone s4s"
Guy2: "cool, i subbed you. now subscribe back! :)"
Guy1: "thanks dude and yes i subbed back"
Both Users receive a subscription.
Quick way to gain popularity and friends on myspace.
It basically means that any comments, messages or pic comments that you leave this person will be returned with the same number of comments, messages or pic comments to you.
This also applies to whoring (see w4w) and spamming, where the idea is to keep clicking "Submit Comment" repeatedly so that your comment is sent hundreds of times - this makes it look like the other person is more popular than they really are.
Kinda pathetic, isn't it.
s4s!! i have 7.2k friends!! s4s and your friend count will double!!!