No it isn't. It's a peer to peer network, both the client and server are open source, anyone can run a validator, anyone can choose the set of validators they want to synchronise with and anyone can act as a gateway, either professionally or informally between trusted associates.
more like a potential scammer to scammer network no? You trust me to trust them and together we will rip everyone else off.
And difference between trusting BTX exchanges is?
A secondary difference is that the exchanges can't as easily target a single customer. If an exchange decides it won't let you specifically withdraw for some reason, you are pretty much stuck. If a Ripple gateway does the same thing, you can just trade your assets at that exchange for assets issued by a gateway that will let you withdraw. You can move funds into or out of a gateway without needing that gateway to perform each operation or subjecting it to arbitrary and unpredictable rules.
If you hold Bitstamp assets on Ripple and decide that for some reason you don't want to hold them anymore, you can sell them for XRP immediately without having to ask Bitstamp to perform the transfer.