My MAF sensor failed on my car as well, but it was when the car had a stock air filter, before I switched to the K&N. There are multitudes of MAF sensor failures that have been reported on this site, but I haven't seen any real evidence that shows the K&N filters are the cause any more than poor OEM parts quality, or general design life of the MAF sensor.
Still, I have to say that the K&N isn't all that wonderful, and I wouldn't recommend it. I haven't noticed any increased performance or mileage over stock. I have noticed a change in the car's performance when I clean the K&N - meaning that when the K&N is dirty (in my case it had about 20k miles) it degrades the car's performance. So I will likely clean mine more often, though the cleaning process is a bit painful since the filter has to dry after a water rinse and again after it is oiled. If the car is needed while cleaning the K&N a different (usually stock) filter needs to be put in temporarilly; this means you change the filter twice each time you clean the K&N. I don't know how many more cleanings I will do on mine; since I've already made the investment I will likely stick with it. But half way through the last cleaning process I felt I had made a mistake giving up the simplicity of running the stock filter.