Is it that farfetched?
How many teams have shaky quarterback situations where Favre would immediately play? Obviously he's better than many QBs, but that doesn't mean for instance that the Raiders would get him over JaMarcus Russell.
Let's look at all 32 teams
New England: NO
New York: Maybe
San Diego: NO
Kansas City: Maybe
Tampa Bay: Maybe
New Orleans: NO
San Francisco: Maybe
St. Louis: NO
So that leaves Buffalo, the Jets, Miami, Baltimore, Kansas City, Washington, Minnesota, Detroit, Chicago, Tampa Bay, Carolina, Atlanta, Arizona, and San Francisco.
Throw out Minnesota, Detroit, and Chicago because they're all in the NFC North, and Green Bay won't trade him there.
Throw out San Francisco, Atlanta, Kansas City, and Miami because Favre won't want to play for a bad team.
Throw out Buffalo because they have confidence in Trent Edwards.
Throw out Carolina because they have confidence in Jake Delhomme.
Throw out Arizona because between Matt Leinart and Kurt Warner, they have someone who can play a little.
That leaves Washington, Baltimore, Tampa Bay, and the Jets. The only reason Washington is listed is because Dan Snyder is their owner. If he wants to stick with Jason Campbell, they won't make a play. Baltimore makes a lot of sense at first glance, but will new coach John Harbaugh really want to use Favre for one season and then start all over again next season?
What about Tampa Bay? Jeff Garcia played well for them last season, and they already have Garcia, Chris Simms (though he wants out), Luke McCown, Josh Johnson, and Brian Griese on the roster. If Jon Gruden wants Favre, they'll probably get him, but if he sticks with Garcia...
...then that leaves the Jets. Between a wide open quarterback competition and a pretty talented team at other positions, the Jets are as good a fit for Favre as there is. Kellen Clemens can learn for a year under Favre, and then hopefully take the job next season, while the Jets can move Pennington for a late draft pick.
I have no idea if the Jets will actively pursue him, but to the doubters, it makes more sense than you might think.