• no support for private message (pubsubhubbub, anything atom-based) • inability to move relationships when changing service • no standard API for application interaction
by leaving each of these (and others) out of scope see: http://ostatus.org/sites/default/files/ostatus-1.0-draft-2-s... they have created an ecosystem unfriendly to developers (who have to approach each provider separately to work out auth schemes and APIs) and likely to lead to vendor lock-in (because relationships can't be transferred and basic features are implemented differently in each system).