Why is it that at this particular historical juncture numerous churches—Catholics and Orthodox largely excepted—have changed eucharistic admission policies that prevailed throughout the preceding tradition? Why is it that Derridean pure hospitality has made huge cultural strides at precisely the same time that we have witnessed the loosening of eucharistic guardrails? And why is it that in the wake of Lambeth 1968, Protestants increasingly question any kind of eucharistic boundary? 
We should be aware what is at stake when we apply the notion of pure hospitality to the Eucharist: It is the erasure of ecclesial boundaries and hence of ecclesial (or confessional) identity. If, as Henri de Lubac used to put it, the Eucharist makes the church, then a boundaryless Eucharist makes a boundaryless church. Pure hospitality applied to the Eucharist implies a universalism of the worst sort: It is the radical insistence that the church is without any positive identity whatever.
Source: Open Communion Invites the Devil to the Table | Hans Boersma