Whether Netflix violated the persons privacy or not is debatable (hence it hasn't been settled yet), however they certainly don't appear to have the intent to keep peoples privacy:
> The suit is also asking the court to stop Netflix from launching its promised second contest to improve the recommendations — this time giving out user data that includes ZIP codes, ages and gender, along with movie ratings and ID numbers substituted for user names.
I'm not certain how ZIP codes work in the US, I know however that my postal code for my childhood home in the UK could place me within a 30 house range on my street. Given age you could extract this down to ~7 people, given sex it was down to 3. Being 1 of these 3 people means I have a 50/50 chance of identifying two 'anonymous' people based solely on postal code, age and gender.
Lawsuits usually come down to intent, and Neflix arguably doesn't have the intent to keep its users privacy if it's intending on releasing ZIP, Age and Gender information.
This means, on average, you should still be able to place someone down to ~5 people. God forbid you're a 110 year old using netflix. If netflix is releasing it in 5-year groupings that still puts you in a group of ~30 people for grouping of ~30,000.
I'm unsure if any data release like this counts as anonymous.
Also, it's normal to add / remove ~1% of your sample to remove some edge cases and muddle the waters.
So why sue netflix instead of IMDB? Additionally, is there an expectation of privacy when posting movie reviews to public websites?