When it was announced six weeks ago that the chief executives body Acevo was going to move next year into the building owned by the National Council for Voluntary Organisations, both parties were careful to emphasise that this was not a first step towards a merger.
But the move has inevitably led to widespread speculation that living under one roof will in the longer term lead to much closer collaboration, if not actual merger. People are discussing whether that would that be a good thing for the sector.
There is some similarity between the missions of the two outfits: the NCVO's expressed purpose is to give "voice and support to civil society", while that of Acevo is to "support, connect, develop and represent" chief executives, trustees and senior managers.
Their style and focus, however, are very different. The NCVO is measured, consensual and politically cautious, whereas Acevo is more prepared to go out on a limb, especially when it comes to the question of public service delivery by the sector.
Those differences are, to a great extent, a function of the personalities of the two leaders, Sir Stuart Etherington and Sir Stephen Bubb, whose well-known rivalry seems to have relaxed somewhat recently. But they nonetheless represent genuinely different aspects of the sector.
A coming together might produce a better deal for members: Acevo has nearly 2,000, all of whom join as individuals; the NCVO has about 8,400 organisations on its books. There is a certain amount of chuntering about forking out twice, and Whitehall would no doubt also find it more convenient to deal with - and help to fund - one organisation rather than two.
The danger in merger would be the homogenisation of debate. That would go against the sector's ethos of fostering and celebrating difference and diversity. But the tide of the times is towards pruning and rationalisation, not least because, for the foreseeable future, there ain't going to be a lot of gold in them thar hills.