Even with ringsize 10, it does not help if someone does BTC->XMR->BTC with the same exchange (or an exchange that shares records) without adding some XMR->XMR churn steps inbetween.
My future freedom depends on me getting this right, so I am a bit sensitive on this topic. It took me a while to cut through the fluff and figure out how to churn enough to make it safe. Fortunately I also used multiple Bitcoin mixers on both sides and didn't originally get our Bitcoin investment in a way that's directly linked to any of our identities.
It is somewhat irresponsible of Monero's marketing to make such grandiose privacy claims at the moment. I say this as someone that loves Monero and thinks their team is fantastic, and I'd bet Monero will be the privacy currency winner if it isn't already.
