Steven Smith posted this very intelligent article: Tip For Employees - Don't Stop Looking.
But do take heed to his warning! Just a couple years ago I was working for a "Manager" who called me into his office and was very upset that I had posted my resume on Monster.com.
Even after I explained to him that my resume had been on there for a long time and I had just recently had to update my contact information on it, he still took offense as if I was stabbing him in the back or something.
Ironically, just as Steven points out, there were many other reasons aside that would just a short time later really bring home the fact that I was "better off to be rid of them"!
I would never let this risk prevent you from doing the leg work necessary to keep up with the current market, if for nothing more than the networking contacts.
You owe it to your family and your career to be aware of any possible opportunity that could benefit either.
The loyalty factor has to come from both parties and it was proven to me many years ago that even though I believed that was the case and turned down many potential opportunities, you can still wake up right before Christmas with the added worries of looking for another position. I was told that I was lucky to have not been "Laid Off" and was quoted every excuse from the economy to the weather, but that doesn't help a 30% pay decrease look any better.
Don't let yourself fall victim to that type of situation!
Stay motivated! Stay productive! Stay hungry!