I use it for fun! ;-)
Most of the time it's negative. For example, if someone went to a boring party they would sarcastically say "Oh yeah, it was a blast" I've heard it used the other way around, which would be going to a fun party and saying something like "Oh yeah, it was a drag" but it's hard to tell if it's sarcasm or not.
sometimes people scream when they hear good news. expressio of joy,
mohamed....it's said sarcasm not scream -argh-
it realy depends who said it if it is your best friend you'll know that they are just teasing you. but is it is someone you just meet you may tack it the wrong way.
I really think it doesnt matter if its negative or positive, i just think it depends on how somebody says .
As if that's going to stop sarcasm...