It is equally hard not to throw up one's hands and give up today, a few days after Marion Jones made it official — she's a fraud and a liar. Just as Bill Belichick "misinterpreted" the NFL's rules, Barry Bonds still says he thought it was flaxseed oil, none of the riders in the Tour de France knew what was in their water bottles, and Tim Donaghy was a rogue official.

And that's just this past summer, the Summer of Cheating.

Formula One fined its top team, McLaren, an incredible $100 million last month for allegedly using stolen designs from McLaren's chief rival, Ferrari (though that fine may wind up being a paltry $30 million or so). NASCAR teams, including that of the current points leader, Jeff Gordon, were docked points and fined $100,000 after their cars failed inspections before a June race, their front fenders altered from the specifications for that sport's uniform Car of Tomorrow.

An August tennis match involving the world's fourth-ranked player, Nikolay Davydenko, which drew unusual betting interest on Davydenko's opponent, still is being investigated. (Davydenko, who retired in the third set of the match with a foot injury, denies being involved.)

Andy Murray, ranked 19th in the world, told BBC Radio this week that it would be easy to fix a tennis match, saying, "It's difficult to prove if someone has tanked a match or not tried because they can try their best until the last couple of games of each set and then make mistakes, a couple of double faults, and that's it."

And that's where we are, after the Summer of Cheating, the Big Con, a flood of fraud that has pockmarked sports like virulent acne, threatening to take our bread and circuses and make them no more legit than a three-card-monte table on Eighth Avenue.

This isn't naivete. Colleges pay players and pitchers doctor baseballs, and there are equipment managers who make sure some basketballs are inflated a little too much if their team's point guard likes a high dribble. Of course, more than a few boxers put liniment on their gloves, and some goalie sticks are sometimes an inch or more longer than they are supposed to be, and the unspoken motto in stock-car racing is, "If you ain't cheating, you ain't tryin'."

But the corruption seems so massive these days, reaching to the highest levels of almost every sport, making us doubt just about everything we see. Can I tell you that there aren't any other NBA referees involved with mobsters, shaving points almost invisibly? I cannot. Can I tell you that the Patriots won their three Super Bowls on the level? I think they did, but I didn't think the Panthers team that beat the Eagles in the 2004 NFC championship game had a bunch of players on steroids, either.

And what are we supposed to tell our kids?

Marion Jones wasn't some run-of-the-mill sprinter. She was the dream date at the 2000 Olympics, the perfect combination of speed, strength and beauty. Who didn't love that smile, that competitiveness? How many 11-year-old girls watched her float down the track in Sydney, winning five medals, and dreamed their own big dreams? What do we tell them about their months — maybe years — of hard work, dedication, sacrifice? That they should just grow up?

The protectors in every sport say, well, that's just an isolated incident, nothing really wrong here, please come back with your wallets open and your minds closed, and then stick their heads in the sand. It's much easier to rail against the Texans' Travis Johnson for taunting an unconscious Trent Green than to find out just how prevalent coach and player cheating really is in the NFL.

Here's a guess: a lot.

Say what you want about Michael Vick — and you'll surely say a lot after this next sentence fragment — but at least he admitted what he did, put his $140 million contract on the line, and is walking to jail like a man.