A while ago I used Amazon to buy some electronic equipment and a gift for my niece. When I returned to the site the incredibly complex algorithmic stuff which made their recommendations concluded I was the sort of individual who'd be interested in pornographic DVD's and Peppa Pig books.
Thankfully nobody was peering over my shoulder otherwise they'd be left with the impression I was someone who buys nothing but bongo flicks and children's literature. Also imagine I really was buying skin flicks, it certainly wouldn't be the sort of thing I would want passed around.
This was just after one buy over time I'd imagine they'd have a more accurate picture to an almost creepy extent. Imagine the crap Google knows about you, but hey if you are not doing anything illegal, you've got nothing to hide, right kids? What if this information leads to them concluding you are gay, lesbian, bisexual or transgendered you night be bothered.
A woman in the American state of California is most certainly bothered and is suing Netflix (I guess the UK equivalent would be Love Film) for breaching her privacy after exposing her rental history to outside developers who could make a educated deduction (using sources like IMDB) that she was a lesbian, something she would not like to widely known. I speculate what DVD's would lead someone to conclude they were lesbian, the complete Prisoner Cell Block H box set perhaps? I'm drifting into lazy stereotypes I'll admit, the point is if exercising your right to remain in the closet (and even those not) remember finger prints will be left online even if the evidence is cleared out from the local computer.
Yes if you're trans you'll know this as you cant obtain a licence to tranny without IT knowledge.