Socialising, trust in the work context, and diversity

Pretty much all organisation run social "team-building" activities, from informal drinks, team/office parties, to more formal off-site adventure course type events.

The idea is that this will develop social cohesion and allow personal trust and favours to smooth over bad or unclear work protocols.

I've always been somewhat sceptical of this.

Does trust transfer across context?

The fundamental assumption is that trust developed in the non-work-specific context will transfer to the work-specific context.

Is this actually true?

When I think of trust in a work context, I break it down into two aspects:

1. Competence: Do I trust that the person is capable of doing the work?
2. Expected behaviour: How do I trust the person will behave?

Will a non-work-specific social activity develop trust in work-specific competence?  Does a person's behaviour in a non-work-specific social activity develop trust in their work-specific behaviour?

It seems reasonable that some aspects would transfer but surely not all of it would be relevant.

Does a focus on socialising discourage diversity?
Even if trust actually does transfer from social to work contexts, if we couple team membership to ability to socialise outside of work, does this act as a force towards team homogeneity?

Imagine that instead of focusing on socialising, we focus more on developing our trust in mutual competence (practicing together, actually working together) and developing our trust in expected behaviour (agreeing on team interaction protocols).  So even if I hate the person, as long as I trust s/he is competent and we both have agreed to interact in a particular way, then we can work effectively together.

The consequence is that now we are not limited to only working with people we like socially.

What happens with the diversity of an organisation when we change the balance between personal trust and protocol trust?