These two categories of housing have been around for a long time. The idea of "social housing", originally council housing but later extended to Registered Social Landlords (typically Housing Associations), was well-intentioned but perhaps inevitably led to the so-called sink estates of recent decades.
Then, along came New Labour, and they devised a new category of "affordable housing", which was intended partially to offset the huge housing price bubble they had encouraged, making housing unaffordable for the lower-paid. The rest of this idea, which includes not only rented by part-owndership of one's home, was in reality to skew cheaper housing toward those who were a large part of Labour's core vote - the public-sector, highly unionised typically left-leaning employees within education, the NHS and others, whom Labour termed "key workers".
Now, if one just looks at this superficially, one can be forgiven for thinking this is a Good Idea. Some of it wasn't bad in a way, but far more deserving cases missed out because of the "key worker" priority.
Of course, as nothing comes free, it means (as always) that others are having to subsidise these people. In effect it is a hidden effective increase to their often already-inflated incomes (quite apart from gold-plated and generous final salary pensions and other perks) as has been very well documented in recent years.
With a little research, I could provide dozens of links to authoritative online resources confirming this. I well recall from my own (short) time working in a central government department how well known this was there.
My blogging mentor, John Ward, has already blown much of the fabricated arguments out of the water anyway, some four years ago. In his council area, the local Labour councillors wanted forty percent of all new housing to be subsidised by the taxpayer and the other sixty percent of house sales (which would obviously be over-priced to pay for the subsidy to those other 40%).
Thus making provision for "affordable housing" is a kind of tax on the rest of us to make Labour's core vote within the ranks of the employed (i.e. distinct from the benefits dependants) eternally grateful for Labour's largesse and reliant upon it, if not any longer for themselves then probably for their offspring. It also helped to inflate market-based housing pricing, which explains some of what happened in the market during the past decade or so.
Michael Meacher MP today decries the expected (though not confirmed) cutting of public expenditure on "affordable" housing (though the term is erroneous, as if the properties had not been affordable no-one would be buying them, yet how many stand empty?) and inadvertently reminds us of all of the above facts when we think about what he really means. He is in reality decrying the turning-off of the tap from the taxpayer to subsidise a large chunk of Labour's tribal electorate.
His rant is full of transparent rhetoric, though much of his target audience will not be alert enough to realise it, so he'll get away with it there, preaching to his choir. The rest of us should, though, realise what is really going on with "affordable" (a.k.a. "social") housing, and not be taken in by "Meacher the [lefty] Preacher".
The scrapping of a poor and very expensive purely politically-motivated system designed for self-gain by Labour is, overall, a good move. With housing costs starting to head back to where they should be, the artificiality of the last dozen years will be unravelled and we shall all be on the same footing of having to earn the appropriate level of housing for ourselves. Now that is real "fairness"!