Allegations that champion cyclist Lance Armstrong used performance-enhancing drugs have been around for years -- and they surfaced again today as the U.S. Anti-Doping Agency brought formal  charges against him. 

Armstrong denied the allegations, but the seven-time Tour de France winner wouldn't be the first pro athlete to be punished while proclaiming his innocence.

Still, it would be sad to see Armstrong's good works sullied. He made a remarkable recovery from cancer -- a compelling tale chronicled in the book "It's Not About the Bike." And he has combined that tale with his celebrity to create the Livestrong Foundation, which has raised millions of dollars to battle cancer. I'd hate to see that momentum collapse.

Armstrong responded in a statement that read, in part: "These are the very same charges and the same witnesses that the Justice Department chose not to pursue after a two-year investigation. These charges are baseless, motivated by spite and advanced through testimony bought and paid for by promises of anonymity and immunity. ... I have never doped, and, unlike many of my accusers, I have competed as an endurance athlete for 25 years with no spike in performance, passed more than 500 drug tests and never failed one."