I know there are transaction fees. I meant friction as--once you have BTC in a wallet, you are absolutely free to spend them as you wish. There is no way for anyone to prevent a transaction.

Bitcoin addresses are public but anonymous. But yes, you can analyze the public ledger to tie known data (publicly-posted donation addresses, etc) to try to de-anonymize someone. There are coin tumblers/mixers in place in some markets, although it's hard to tell how effective they are.