It can be a problem for any car with a MAF unit, whether it be a 1.8T, 2.8, or whatever.
Basically the operative part of the MAF is a wire/filament that increases or decreases in heat in correlation to the amount and velocity of air and passed over it. Then this value of heat is fed to the ECU, which in turn balances air, fuel and various other parameters accordingly. If the MAF gets gunked up it loses the ability to translate air flow into temperature accurately. Subsequently the ECU receives inaccurate instructions. As Auroan says, you can end up with dodgy performance.
The argument against oiled filters is that the oil can quickly contaminate the MAF, and therefore cause bad running. However, it's something that is often debated. Many people swear blind that it doesn't make a difference whether the filter is oiled or not; others see oiled filters as the work of satan himself.
I personally think that using an oiled panel or cone is probably ok, provided you don not over-oil the filter. Also, the MAF can fail for a number of other reasons. I think mine is playing up at the moment and my induction is completely standard.
At the end of the day, I think it's 50/50. Don't over-oil the filter and keep an eye on any flat-spots or hesitation. If you do end up with performance problems then check the MAF. But I'd put money on the chance of some people never experiencing MAF problems due to oiled filters. But then again, some will.
Drew.