I do not think that they are targeting PC's at all. It is just a by-product of controlling what goes out over the air.
The FCC will not be ordering which programs are to be flagged or not, they will leave that up to the individual stations, and it will be up to them to either flag it or not.
The bottom line is that if you want a DTV tuner card, buy it before next July. Anything purchased after that and you will be at the mercy of the stations as to what you can record.
And as for the illegal movies on the internet, if they were made with a camera set on someone's lap, it won't be flagged and thus would be viewable on any device made before or after the cut-off date.