You're the product even if you are paying for it. You don't think for-pay services won't try to make more money or gain more value from the data you're providing them?
For-pay services have an incentive not to do something with my data that upsets me enough to leave. Let's say an advertising company offers eTrade 50-cents for info on every trade I make. That's free money for eTrade right up until I, as the client, decide that's intrusive and take my business elsewhere. Now eTrade is out my $10/trade, let alone the 50-cents.
But you don't have that leverage with a free service. To them, (in the long run) making some money at the cost of pissing off their customers is better than making no money at all.
But you don't have that leverage with a free service. To them, (in the long run) making some money at the cost of pissing off their customers is better than making no money at all.