Bitcoin strongly enforces two concepts - high anonymity and no chargebacks.
Because of high anonymity, it is nearly impossible to be 100% certain who you are sending Bitcoins to. In the end, the Bitcoin address is just an arbitrary string of characters.
Because of no chargebacks, once you send someone Bitcoins, they are irreversibly theirs (assuming no double-spends and no 51% attack). You can't later recall the money you sent this way.
When someone would buy Bitcoins with a credit card, they could wait until the coins appear in their wallet, and then claim that their credit card was stolen used by someone else to purchase Bitcoins without their intent. They could get away with their chargeback claims, as it would be impossible for the seller to prove that they sold the coins legitimately to the person. Moreover, the seller wouldn't be able to get their Bitcons back due to "no chargebacks" rules.
What makes it different from services like iTunes and the like, is that the value of the Bitcoins is close to how much it costs the seller to aquire and sell them, whereas iTunes' costs are marginal. For example, buying a 1$ song from iTunes would mean that they have to probably spend less than a penny processing everything and providing you content (logging transaction, letting you download the song, etc), whereas if you send 1$ in Bitcoins, you are sending about 1$ worth of goods. When iTunes gets charged back, they lose a penny and can still sell the song any amount of times. When a Bitcoin seller gets charged back, they lose a dollar and can't sell the same coins again.
Bitcoins can't be copied and distributed to multiple people at marginal cost, that's what makes chargebacks so costly for any potential sellers.