How do I know I can trust you and your site? If you are legit, then how can I trust you won't pull a Target or Home Depot on me? Assuming I use your service t

How do I know I can trust you and your site? If you are legit, then how can I trust you won't pull a Target or Home Depot on me? Assuming I use your service to buy something with an account I already have with one of your partners, how do you keep all that secure so you're not exposing way more than just my credit card data?