So I'm with you — there are real tradeoffs here, and I'd encourage everyone interested in this stuff to mull them over (and I'm also happy to discuss: [email protected]). But one thing I really respect about the Stellar organization is the very deliberate approach they've taken to these choices, and how they've found a happy middle that feels like a translation of the existing physical world into the new digital one. If it works, I think it'll make Bitcoin and other digital currencies even more successful.
The fact that this weakness does not appear in the BitCoin protocol, but is rather implied by the human desire for convenience and marketplaces, doesn't make it less of a flaw. One can sneer at everyone who lost money with MtGox for "choosing poorly", so to speak, but on the other hand exchanges are the driving force behind BitCoin's success.
So let's say I choose to not trust any gateway and their currencies, and instead decide to transact in the native stellar currency directly. This is a strange choice: why have support for alternate currencies if the Stellar protocol in itself can do nothing to help gateways gain trust? You might as well have, say, Amazon not even bother becoming a gateway issuing their own USD_Amazon, but instead Amazon would just accept the stellar currency directly. In this case I am still required to trust the native stellar currency. I am required to trust that Stellar --the nonprofit organization-- will correctly follow their mandate (https://www.stellar.org/about/mandate/): distributing x% to X, y% to Y, etc, properly thwarting fraud attempts from people with many fake Facebook accounts, properly thwarting fraud attempts during voting (https://www.stellar.org/about/mandate/#Stellar_creation), properly thwarting fraud attempts from people building fake nonprofits to attempts to gain a share of the 25% of stellars reserved for nonprofits, etc. And Stellar trusts Facebook, so I am even required to trust that there is no malicious employee at Facebook that will exploit APIs to attempt to gain stellars. You plan to distribute stellars through SMS? Heck I now need to trust telecom carrier employees, etc. Even if you are honest and make no operational mistake, fighting all these fraud attempts will be a large uphill battle, and there is way too much trust required, way too many possibilities for mistakes to happen.
Contrast this with Bitcoin: all Bitcoin requires is trust in three cryptographic algorithms which fit in a few thousand lines of code (ECDSA w/secp256k1, SHA-256, and RIPEMD-160).
I appreciate the attempt of building a different payment technology, but Stellar should not mislead people into believing they are similar to Bitcoin ("Stellar is decentralized [...] owes a lot to Bitcoin"). Stellar threw away the most fundamental element of Bitcoin: complete decentralization (including decentralization of the issuance of units of currency.)