They don't gather all your likes and dislikes to match you up.
They gather this information and use it to tailor marketing to you.The parent company distributes ALL your info for marketing lists.
You can also do a whois search in the site WhoisXY.com and know the owner, technical, administrative contact details etc.. you can use the phone number or email id which you get in whois search and try to contact the person and clarify your doubts.
If the site has SSL certificate it is good site for transactions. SSL certificate enabled site looks like https://paypal.com.