That and it will let more dirt into the motor, so you'll want to keep it in check. I think they intend it for race use in a controlled environment where you won't be running in dust storms or whatever. I haven't used one myself, but that's what I've heard.
I run the BMC race filters on a race engine. The full race filter does let alot of particles through it. I would recomend using the street version unless you really like going through and freshening and rebuilding your motor every couple of months.