My daughter took a field trip to the International Manufacturing convention. She was very excited by all of the robotic machines, but then one of the exhibitors brought out their skimpily clad dancers to the stage. Men flooded the exhibit, taking pictures with their cell phones and calling their friends. My daughter was so offended (her first trade show) that she yelled at the dancers for being traitors to their gender. I would like her to be able to consider a career in engineering/technology, but this behavior gives her a hint of where she won't be welcome.
I haven't been to an Open Source conference (unless you count Usenix in the 70's), but most shows won't work financially if there aren't exhibitors unless they or are held in free space such as a university. Exhibitors and universities are generally sensitive to people who are offended by this sort of activity. Letters to exhibitors or universities will frequently put pressure on the organizers to discourage this sort of antisocial behavior. If the behavior comes from someone who works for a corporation, a letter to that companies HR department is also likely to be effective in either getting the person to change their behavior or leave the company. Most companies don't want their employees representing their employer poorly. My company has a policy that employees can't visit a strip club while away on company business, even on their own time and expense, nor may employees expense such trips locally. While one would think this would be a big problem, sales teams will do almost anything to close a sale. Having a company policy makes it easier to tell a client no, that it's against company rules. I'm sure they wouldn't want an employee who was groping people at a convention either.
If you know of a conference which has been problematic, writing letters to the venue and exhibitors will be a proactive step in getting things to change. Having both men and women raising the concern is helpful when the venue or exhibitors incorrectly think that someone is just overly sensitive.