There's been speculation ever since Spain won the World Cup that Cesc Fabregas was set for a move back to Barcelona.
While Fabregas insists he is happy at Arsenal, you have to imagine he'd leap at the chance to return to the club where he first learned to ply his trade. Fabregas, along with Messi and Iniesta, is a product of Barcelona's youth system known as La Masia.
Barcelona plays a distinct brand of football that favors short passing, possession, and build-ups off short passes. Players at La Masia are instructed in this brand of football starting in their teenage years. The idea is to enable them to fit into the first team seamlessly should the opportunity arise. This is a strategy used by the famed Dutch academy Ajax as well.
Sky Sports has reported that Fabregas's teammate at Arsenal, Denilson, could also be poised for a move to Barcelona. He's cost quite a bit less, is young, and would probably fit in well at the club. He also isn't getting regular first team experience (which he likely wouldn't get much of at Barcelona either).
Considering Barcelona's debt issues, it's questionable whether or not they can afford a player like Fabregas (despite the influx of cash from their Qatari sponsors). Thus a move for a similar player, on the cheap, might be in their best interests.
Still, Barcelona is the best team in the world. Why they need to add anyone is beyond me.