From what I read on Twitter, it seems there's a bit of confusion regarding SMOB. Indeed, while SMOB provides a framework for Open and Semantic Microblogging, it does not define a new protocol, but simply uses SPARQL/Update over HTTP to exchange information between hubs (posting / removing notices and following / followers). Hence, this is not something that competes against OMB, the OpenMicroBlogging specification.
Actually, OMB is something we planned to look at for a long time, as briefly discussed when Status.net / OMB was presented in the W3C Social Web XG telco. I've finally took the time to analyse the full spec and checked how it compares with the distributed microblogging implementation of SMOB, and more generally with the vision of Semantic Web / Linked Data (SW/LD) microblogging services.
So here is a proposal for "Semantic OMB" (on Status.net wiki) that describes how the current OMB protocol fits with the previous idea. In particular, it aligns the terminology with existing classes / properties from well-known ontologies, and discusses how some current parts of the spec should be updated. It also discuss how OMB operations can be mapped to SPARQL/Update queries, based on the ones that currently happen in SMOB for cross-hubs synchronisation.
As you can see when browsing it, besides the terminology mappings, most of the things are compliant and there are only a few things that shall be discussed, in order to:
Thanks to these small updates, it could provide a protocol enabling SW/LD systems to be designed based on the OMB protocol, while having a sufficient abstraction level to comply with OMB systems using other technologies for data modeling and exchange. I'd be more than happy to see such features in an upcoming OMB release, and hopefully see deeper links between OMB and SW/LD efforts, as both aims to achieve the same goal of openness and interoperability. Comments and feedback are welcome on the related thread on the OMB mailing-list.