With K&N filter, if the filter is over-oiled or the filter is put in without letting the filter completely dry can foul the MAF and cause lot of problems. This is the single most draw back of a K&N filter. Meaning, the user must be careful when cleaning and oiling the filter. One has to ensure that the filter's oil is completely dry before putting it on.
On the other hand, with a regular paper filter, no chance of fouling the MAF (because there is no cleaning/oiling of the filter; you would just replace the filter).
There are lot of people buying all kinds of after-market products (fuel saving magnets, turbo/twisters in the intake, etc.) If they are happy to spend that money, why should others have any issues?
Agreed. I think that the K&N was a good investment for me. It was $50 shipped. I have put 120,000 miles on it and still have half the cleaning kit left. To compare, the paper filter was $26 and should be replaced every 20k.
At 187,000 miles, my car runs great, does not use oil and with the filter and in my case, uses less fuel.