Seems obvious enough - mixing adult men, many single, with teenage girls with inadequate supervision. The Scouts have rules, but if people don't follow them, this is what you get.
Not just adult men with teenage girls, but adult men with teenage boys. From the article:
In Haltom City, Texas, former police officer John Ross Ewing, 28, was indicted by a grand jury in March on charges that he sexually assaulted two male Explorer scouts, ages 15 and 16, at his apartment.Yet another reason to keep gays out of the Boy Scouts.