U2

Bitter feuds and rivalries among some artists could make for some uncomfortable moments at the 48th annual Grammy Awards as battling stars attend the same ceremony.

Grammy Awards executive producer Ken Ehrlich tells TMZ that anyone looking to start trouble on the show should be warned they could ruin their chances of being invited back. "We've had opportunities on the Grammys to have controversial moments and I don't do it, because I don't want the lead story the next day to be about [the controversy] and not who won awards."

Here's a look at some of the rivalries and feuds that could make the Grammys a showdown to watch:

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• Madonna
• Coldplay
• U2
• The Killers
• Kanye West
• 50 Cent
• Gwen Stefani
• Jay-Z
• R. Kelly

A first show by the Irish rockers sold out on Jan. 16, but organizers were forced to regroup after the 12 stores selling tickets experienced computer problems and were overwhelmed by massive crowds. Police had to be called in to restore order when some infuriated fans threatened to break into the stores.

The supermarket chain that owns the stores issued a public apology following the mayhem, which kept some frustrated fans waiting in lines for more than 12 hours.

Concert promoters set up a telephone call center to handle sales for the second show, and organizers said in a statement that it handled nearly 900,000 calls on Sunday from fans seeking tickets.

U2 is scheduled to play at Sao Paulo's Morumbi stadium on Feb. 20 and 21, just two days after the Rolling Stones stage a free concert at Rio de Janeiro's famed Copacabana beach. Nearly 1 million people are expected to attend.

Bono said the money would go to the Global Fund to Fight AIDS, Tuberculosis and Malaria.

"So, here we are, fat cats in the snow, and I say that as one," he said to laughs. "It is a great place to do business and we have some business we want to talk to you about."

"Red" includes red-theme products from American Express, Converse, Gap and Giorgio Armani.

The venture will include an American Express card, shoes, T-shirts and sunglasses and is meant to be a long-term fund-raiser for the group, fund executive director Richard Feachem said.

The three were chosen for their individual efforts to eradicate disease and poverty in Africa. The Gates Foundation funds projects that focus on public health -- vaccinations, and development of new drugs -- as well as educational projects in the U.S. and around the world.

Bono, who's met with everyone from the Pope to Senator Jesse Helms this year, is well-known for his participation in raising global awareness through concerts like this year's Live 8, which he spearheaded with musicion Bob Geldof. Two things make Bono, "Bono": his outspokenness on global poverty and his signature sunglasses.

According to Forbes, Bill Gates' net worth is around $46.5 billion dollars. As a whole, U2's net worth is estimated to be around $700 million. So it's safe to say it takes money to be generous, but the world is certainly a better place because of it.

Time also named former presidential rivals, Bill Clinton and George Bush Sr., as "Partners of the Year" for their humanitarian efforst after the Asian tsunami and Hurricane Katrina.

It's amazing how friendships can develop when there are no special prosecutors in the room.