I quote, "I wouldn't be so sure... Steam Cards can be sold for real money, which is a bigger deal than when it was only hat crafting. They also made their stance clear against external application that simulate a game being played", from a post.

Here is the link that was posted: https://wiki.teamfortress.com/wiki/Idling#Valve_ban
From that link, I quote, "On the September 2, 2009, blog post, Valve took a zero-tolerance stance against the use of external applications to manipulate the item system, removing all items earned through these applications to date.[1] The announcement stated that around 4.5% of active players would have been affected. All players who had not used external applications were awarded the Cheater's Lament, an all-class hat that appeared as a golden halo. The drop rate for all existing hats was also increased."

From the [1] source: http://www.teamfortress.com/post.php?id=2787
It states, "Over the next few days we'll be removing all TF2 items that were earned using external idling applications. We're going to adopt a zero tolerance policy for external applications used to manipulate the persistent item system. Due to us not having a policy in place prior to today, this time we're only removing the items earned through cheating the system. Going forward, if we find users using external applications, we'll remove all of their items. If you're interested, only about 4.5% of the players in TF2's community will be affected by this cleansing process.

Meanwhile, everyone who took the moral high road will soon be finding a new hat in their inventory. We've also significantly increased the chance of finding any of the existing hats.

We realize there is a high level of demand for items, and we're still working on systems to allow you to find them in new ways (via Trading, and crafting duplicates into desired items). However, we need to draw the line at running external applications."

I want to use Idle Master, badly, but my paranoia keeps stopping me. Should I be concerned at all about this?