I used to work for Nielsen as a field rep. The way they gather the data is solid, but they have some serious issues with quality control. Meaning too much QC. If the power goes out in one section of the home, and the box is reset, the whole days viewing data is thrown out for the WHOLE household. They should just throw out that one viewing site. As for DVRs, the article fails to mention that Nielsen already accounts for DVRs, quite well I might add. It's live+7 days. Meaning that if you recorded tuesdays american idol, and didn't watch it til sunday, it still counts for tuesdays viewing data. How it deals with the nightly numbers was a bit above my pay grade, but i think the DVR equipment tracked the SID codes while it was recording.
Biggest problem Nielsen really has is internet usage. They just (like 3 years ago) started tracking internet sites with their A2M2 program. The sample is very very small, about 1/5th the size of a TV sample. And a lot of the households are former TV sample homes. (they offer them the I2 program as the home comes out of the LPM sample) They also now are able to track distance family members, like kids at college are counted now away from home, but count as part of the household. (figure that one out if the parents live in Minneapolis, and the kid goes to school in LA?)
As for people wondering why Nielsen is a viable company in this digital age? Simple demographics. Nielsen has every household members income, job title, where they work, shopping habits, age, etc. The cable company can find out what a person is watching through an STB, but doesn't have ANY of the demographics of the household. Nielsen using LPM systems can tell you EXACTLY who was watching what at a specific time, including the persons age, wine buying habits, primary shopper in the home or not, and what kind of car(year, make, model) they drive. (yes, these were the questions i had to ask households every 3 months) Obscene target audiences. Even with the old NSI sample, Nielsen had more data than the cable companies. (NSI is total household data, LPM is persons data)
For those really wondering, Nielsen does track homes that pirate satellite/cable. They just don't show that number anywhere. :)