Everyone that is in the business of domaining wants to sell more names, that's common sense. There are domainers that have the best of the best domains who just sit back and wait for offers. Others take a more active approach to selling and do it in a professional manner. Then there are some who are just making things look ugly for everyone. Spammers, sometimes scammers who just send email after email, names of varying value, names they might not own.
There was a thread started awhile back on Namepros that is titled, "Emails from domainers selling crap names" The thread started out as a place for those getting some annoying emails to vent, but now as more people have joined the thread, there is a call for such things as, "Its time to strike back, give them a taste of their own medicine" Posting names and tags such as spammer or scammer so this is what will show up on Google when someone does a search for the person,company or email address.
This is why you don't email other domainers. There is a professional,legit way to contact potential end users, but its rare you are going to sell a name to another domainer this way. Everyone only has so much time in a day and its foolish imo to waste resources on a selling method that will not provide much success.