If I sell you a soda and you give me a dollar and I don't give you the soda claiming you didn't give me a dollar, what can you do?
If "I sell you a soda for $1 to this address: …" and I don't give you the soda, what can you do?
Sure, you might answer question one with some violence towards me or my store.
With bitcoin you have all the benefits of an on the record transaction like credit card payment combined with full anonymity as long as there are no complaints.