Then don't post your ym IDs in any forum section. Bots search forums, blogs and websites to gather informations such as YM IDs. They tend to do these kinds of things to promote their own websites (ie. porn sites). Treat your YM ids and other informations as your precious things lol. Be cautious and/or careful on giving away informations. You can even hacked by a hacker by just giving away your informations.