It's become a truism of sorts that Calgary always has plenty of veterans and no prospects. With most of the best players over 30 (Tanguay, Iginla, Kiprusoff- provided you still think of him as a best player, and until yesterday: Langkow), and few high end prospects, they appear to be a few short years away from having no cheap retainable talent on the team.
This means that when a team with plenty of prospect depth (Tikhonov, Turris, and so on) and a definite need for a player like Langkow comes calling for Langkow, you better address your need for the future. Of course, that's not even close to what happened.
Don't get me wrong: Stempniak is not a "bad" player- he's a flawed player. In terms of actual output, he's a better known Curtis Glencross. He made his name on a high shooting percentage season and having been part of the Toronto Maple Leafs (who will just about make anyone famous), but doesn't drive possession and his upside probably ends at a sheltered second line role.
So let's just go ahead and establish that Lee Stempniak isn't what the Flames really need right now. They have great depth players, from David Moss and Olli Jokinen (yeah, I said it. So what?) to the aforementioned Curtis Glencross and Tim Jackman. In fact, you could argue the Flames have too many depth players, but that's for another article. The issue we find is that either Feaster is targeting the completely wrong players (see also the trade of Robyn Regehr) or is simply unable to negotiate with any amount of skill. Both are troubling, but the latter more so.
So long as you're getting a fair or near fair value for the player leaving, getting the wrong asset back isn't the end of the world. If you identify Lee Stempniak as a player of equal value for Daymond Langkow then go ahead and make that trade- though you'd probably want to assure yourself of how he fits in on the roster. But if the Phoenix Coyotes are coming to you asking for Langkow, you're in a position of power.
At that point you have to force them to help you address a need. When the Calgary Flames went to the Buffalo Sabres with Kotalik and Regehr, the Sabres were in a position of power and used that power. When the Phoenix Coyotes came asking after Daymond Langkow, the Calgary Flames should have been in a position of power to ask for a Tikhonov, Boedker, or a few draft picks, rather than a player who fills no current needs on the team and adds nothing of additional value. Instead the Flames took a player who'd likely been looking to leave the Coyotes anyways, and by and large doing the Coyotes a favor.
In a vacuum, there's absolutely nothing wrong with Langkow for Stempniak given the questionable nature of Langkow; this isn't a vacuum though and there's plenty of questions, such as "Why didn't Feaster attempt to address an actual need?"