The way in which the media formulates a transfer rumor can only be compared to that 'manatee idea ball' piece from South Park.
If you join enough dots you can create a picture that countless gullible people and other news outlets will latch onto and the thing just snowballs. Take this one for example, let's look at how they've derived (I hope) that a move is a possibility.
*Firstly, there isn't anyone trying to disprove it right now (unless of course you include our club/directors etc

)
* Van Gaal is a big fan of his.
*He's exactly the kind of player Utd are missing
*Performed well in the WC (the shop window as they call it)
*United have money to spend thanks to new kit sponsorship etc
*EPL fans add fuel to the fire on Twitter/Facebook
It was the same shit that the Italian papers were doing with Aguero a couple years back. No other country put as much effort into running the story as Italy did. In fact, if I'm not mistake, Sergio even said at one point ''who wouldn't like to play for a big club like Juve'' or something along those lines.
All that said, it would be nice at this point in time (given all this speculation) that Vidal would come out and clear things up real quick, holiday or no holiday, appease the fans!