If you pay with bitcoin your wallet id will be visible to the buyer (actually to everyone). even if you use new intermediate wallets all the time, they will point to your main and you can be tracked. if you use it to mailorder something they can link your address to the id. you can store small amounts in multiple wallets you received them in, but that's a lot of effort and you need to transfer extra for big payments to combine them.

This video is amazing. It's about ~2 hours before the senate of Canada, if I remembered correctly, and I learned a lot!