I am worried by the advice 'use OAUTH' but for a very different reason.
OAUTH and SAML are both attempts to provide a secure authentication scheme that works within the very particular and very peculiar environment of Web browsers. They are schemes that necessarily involve techniques that are rightly regarded as alchemy if not outright witchcraft.
That is fine, that is more than fine if you are developing an authentication scheme for use within Web browsers (or if you are developing whatever SAML and OAUTH are these days, neither was originally billed as authentication). But it is completely inappropriate to ever suggest let alone demand that anyone use a technology whose primary design constraint is to work around the voodoo of _javascript_, URIs, HTTP cookies etc. etc. in an application where none of those legacy issues apply.
One of the big problems of IETF is that a lot of people don't think about how to get their scheme deployed and when they do, their plan is to tie it to some other group as a boat anchor. Back when we were doing DKIM and SPF we had to tell certain DNS folk that the fact that almost no DNS Registrars offered customers the ability to specify new RRTypes was their problem and was going to remain their problem no matter how loudly they tried to complain that it should become our problem.
In the case of OAUTH, there is another problem in that OAUTH really isn't a very open protocol from the standpoint of the user. I can use my Google or my Facebook or my Twitter accounts to log in via OAUTH at a large number of sites. But if I want to use any other OAUTH provider I am completely out of luck. Or at least I will be until this becomes one of the multifaceted complaints in the anti-trust hearings coming soon to a capitol hill near you. And yes, that is a consequence of how the protocol has been deployed, but that probably not going to get people very far on capitol hill.
The Internet is for everyone. The Internet is for end users.
I am really not that interested in who makes the ingredients except to the extent that it determines what sort of cake emerges. One of the unexpected side effects of Web 2.0 has been that it has greatly centralized power in the hands of a tiny number of individuals. Individuals who are at best accountable to shareholders, but in the case of some of them, a separate share class ensures that they are accountable to nobody. In neither case are the people with power accountable to end users because they are not even customers, they are the product.
What I am interested in is the extent to which Internet technologies are Technologies of Freedom. The question we need to ask ourselves is 'does this technology increase end user autonomy or increase their reliance on third parties'.
