Jose Reyes signs with the Marlins. It's not like the Nats were interested (despite what some baseball guys believed) and by itself it doesn't make the Marlins better than the Nats... necessarily*. But a team in your own division making a big-time signing does promote a level of envy.
Layne Nix signs with the Phillies. It's not like the Nats needed to bring Nix back. But he would have been a useful 4th OF, providing lefty pop off the bench, and a team in your own division grabbed him up (let's hope the Phillies have to play him everyday - although it sounds like they'll platoon him which would be perfect for the guy) meaning they are filling up those roster holes while you aren't.
The Nats want Mark Buehrle but so do the Marlins (who obviously will spend), the Rangers (who obviously are in a nice position if you want to make a championship run), and the White Sox (who obviously hold some advantage as the team he has been on for his entire career).
The Nats' Plan B is Roy Oswalt, whose plans are up in the air.
The Nats Plan C is CJ Wilson, who is the Plan A for at least 2 other teams, and is drawing similar interest from attractive teams like the Red Sox who are perennial contenders, and the Angels, who are much closer to his home in Southern California.
If the chips fall the wrong way the Nats could end up with nothing. It would be disappointing but it would not mean that 2012 is any less exciting. This is still a team on the rise and barring injury you have to believe that the 2012 Nats will be better than the 2011 version, even without considering the rise of such players like Bryce, Rendon, and the stable of young arms. I feel like there should be more here to say but there really isn't. The Nats could end up with nothing. It could pretty easily happen. And that's ok.
*The Marlins were bad last year, but had a pretty unlucky year. Outside of rookie sensation Mike Stanton and, I don't know, Greg Dobbs? Who outperformed their expectations last year? Josh Johsnon - who could be as good as Strasburg - was out most of the year. Hanley Ramirez - an all-star before last year - didn't just disappoint, he was flat out bad. With one more signing I could see this as a team that wins 15 more games.