Is this an abnormal rate of spoke breakage? I just broke a spoke and this is the fourth spoke I've broken in the last 12 months.  This one was very puzzling because it came at the very end of an easy 30 mile (48 km) ride.  I was pedaling very slowly into my driveway when it snapped. 

All four have been on the drive side of the rear wheel.  This is a Specialized Allez, one year old, with factory wheels.  I weigh 175 lbs (79 kg) and ride about 2000 miles (3218 km) per year.  Just recreational riding on good road surfaces.

Is this an abnormal rate of breakage?  

And if it is an abnormal rate of breakage, what should I do about it?

EDIT:

I took the wheel into the LBS today. They didn't seem surprised by 4 broken spokes in a year, but everyone else is, so I'm going with everyone else. The mechanic checked the tension and they were all correct with one slight exception, so that's not the issue. The wheels are factory wheels and not exactly top flight. The spokes are 1.2 mm rather than 2 mm, so pretty thin. And they're 28 spokes per wheel, so that's cutting it even thinner from what I can gather. 

Rebuilding the wheels is $125 each, so that's just not worth it. I can find much better wheels for not much more, so I'm on Amazon looking at wheels while trying not to deplete my life savings. (What some people will pay for wheels boggles the mind.)  I'll have them fix the spoke and check the tensioning so I can sell them and ride until I get replacements. 

Gotta buy the tools and learn to replace spokes and true wheels....
Yes, as the comments pointed out, this is abnormal.

I would make the attempt to take the wheel back to the LBS where you bought the bike. The might be able to work with Specialized and get the wheel replaced completely. Once at the LBS, have the mechanic inspect for any external factors (derailleur strikes, etc).

If they can't get it replaced, then I would either: (1) have the wheel completely rebuilt replacing at a minimum the spokes but taking a good look at the rim once it's disassembled...as noted in the comments, it might be warped; or (2) buy a new wheel. Having it rebuilt can often be pretty pricey and you can get a decent wheel these days for a couple hundred.