It does give data to advertisers, but the effect is much more dramatic than you might think. For me, it has completely nuked the advertisers’ profile of me to the point that the mail I get is obviously affected too. I was getting normal mail before using, but then for a few years I was getting senior citizen related mail and travel brochures, now I am getting coupons relating to pregnancies and personal injury ads. Recently I have been getting texts from realtors asking if I want to sell “my house”. Grain of salt is important, I tend to go to random websites, if you have specific interests and regularly and mostly exclusively go to websites related to them, then this scheme would not work. Simply avoiding the ads in the first place would be superior.