If the users are high company executives, all you can do is babysit their machines. Sad but true. Try to give them two computers if you can, so that company information can't be taken. If you can get them off Windows apps that don't run under Wine, see if you can install Ubuntu on their computers. Call it Windows Ubuntu or something. (Is my cynicism showing?)
Other than that, you've got people who have wide internet access who are doing stupid things and causing problems for the company. (Do they have admin access on their computers? Typically, people with a legitimate reason for admin access are educable.) There's got to be something management can do about this: mandate education, cut down on allowable sites, threaten to cut down on allowable sites, whatever.