OK, History lesson!
It was the summer of 2005 when Team America World Police came out.
That was the summer that Kumoricon was first at the Doubletree hotel.
There was a booth in Artist's Alley that really liked Matt Damon, they had a print out of his face hanging in their booth and when asked about it they'd yell the quote (and sometimes kiss it).
It became a tradition among the AA booths and staff to yell "Matt Damon" every now and then, since it was an inside joke for them by the end of the first day in '05.
This year it was a much bigger deal since it was the convention's triumphant return to the Doubletree hotel.
Now the neat thing is that when making Team America: World Police, Trey Parker and Matt Stone had planned on having Matt Damon be sort of a nerdy character, a real smart guy. However, when they got a look at the puppet head they both thought he looked like a retarded person. So they re-wrote the script so that ALL the Matt Damon character says is his own name.
And THAT is why they yell the name.
Here's me and one of the people at the founding booth.