Answering those "Confidential" Ads

As I have been scouring the internet for possible jobs I am noticing more and more positions that are listed by "confidential" companies. Of course these are the positions that sound most appealing to me. However when they are advertising a sales/marketing job, is it REALLY a marketing job or is it for door to door magazine sales.  And when the ad states must have good interpersonal skills, is it a customer service job or is it "inter-personalizing" at a strip club doing a lap dance.  Then if you do find one that may be legit, you are now mailing your personal information and employment history to a PO Box.  Who knows who you are sending it to?  I am thinking it may explain the crazy phone, email, and snail mail offers that I am now receiving asking me to work from home IF I pay them $487 for their "At Home Start-up Kit".  Hmmmmm.