How about that play with Gary Sheffield in the Sox/Yankees game last night? There was a hit into the corner, and while Sheffield is picking up the ball, a drunken fan reaches out and takes a swipe at him. What was great was that Sheffield pushed the guy back, THEN threw the ball back in. He probably would have torn the guy a new one, but he said he thought about Ron Artest being suspended for the rest of the season, so he held back.
Ultimate has a real problem with fan interference at many big tournaments, even Nationals (although in recent years the UPA has done a lot better about patrolling this). Fans and players just crowd the line, making it difficult to throw longer passes that way. (I'm going to start something again with the NUA's Ed about how he probably thinks it would be a great strategy to force line and have your sideline players stand next to the thrower.) And then there are all the tents and metal chairs and coolers. At Fools this year, there were big metal/wooden benches in the 3 yard space between fields. It's a lawsuit waiting to happen.
My old teammate Cork has at least twice "reprimanded" fans for interfering with play at Nationals. In 1989 Nationals, a floater down the line struck a big-lens professional camera and Cork started yelling at the guy. I don't remember the circumstances of the game, as I was with the bestest little team ever, Earth Atomizer. In 1997 Nationals, in a game important to qualifying for semis, we beat Double Happiness by 2. Someone threw me a leading pass in the end zone. I had to get on my horse to catch up to it, then had to lay out for it, so I was focusing only on the disc, but as I'm reaching for it, I'm overwhelmed by a sea of bubbles out of nowhere. Startled, I don't catch the disc. I get up to see a bunch of Bay Area women sitting there giggling, playing with little kid bubble blowers. Cork goes up to them and smacks the blowers out of their hands. They thought it was funny. If any of you interferers are reading this and would like to apologize, I am willing to forgive and put it behind me. I have a vague memory of a tight call that game that went against Double, but can't remember what it was or I thought it was a bad call. Anyone remember that either?
Golf has occasional problems with fan interference, but generally it is to the player's advantage when the fans get in the way of speeding balls and stop them from getting into more trouble. But then you have those idiots screaming "Get in the hole!", or people yakking on cell phones, or photographers snapping pictures while players are in their backswings or downswings (P.G. Wodehouse wrote of a golfer who was distracted by the sound of butterflies flitting in an adjacent meadow). Now, before you scoff about how football players have to deal with 80 000 screaming fans, it's different because what is startling is the level of noise above the background or the change in the noise level. If somehow everyone stopped screaming at the same time, I bet a quarterback would throw the ball over the receiver's head from the surprise.
Some are more temperamentally-prone to this distraction than others, and I don't think it's just a case of being morally stronger if it doesn't bother you, any more than not needing glasses is a sign of strong character.
I think the best/worst case of fan interference was in the surprisingly hilarious movie "Happy Gilmour", when Happy was in the process of winning something like the US Open when a fan ran him over with an automobile on the fairway during the round.