Well said, DS64till.
My local food bank only takes referrals too, but even if all of them were 'free for alls', so what? People talk as though it is their money being spent. It isn't - they use donations from people who choose to give to those less fortunate. If the people sneering at the nails or apparent lack of neediness of the users felt like it, if theirs is a non-referral bank they could use it themselves.
Poverty shouldn't attract the scrutiny and disapproval of others on top of all the other indignities it brings. I've seen comments complaining about people using charity shops who don't 'need to', too, and people offering unwanted items on FB or Freecycle and saying that they only want them to go to someone 'in need'. If you donate something, IMO it should be given freely and without conditions.
If charity shops and Freecycle-type schemes are designated as only for 'the needy' they will have a stigma that will deter those in need. Yes, there are 'grabby' types who take without giving, but it would be a shame if people refused to donate on the offchance that their items would go to someone they see as undeserving.
Also, not applicable to foodbanks, but a lot of people seem to think that offering old 'stuff' is a favour to the recipient, whereas that is often just a side-effect of their reason for donating. Mainly it is because the item is no longer any use to them, and getting rid of things is not as easy as it used to be. The council charges £25 an item to take things away, tips are often inaccessible and closed several days a week, and deliverers often can't take old items away when they bring new ones. Donating is very often a two way street.
I wish there were more honesty about things like this. the government bangs on about 'targeting' as an excuse for having less social spending, and the idea that there is a large number of 'scroungers' who sponge off the rest of us has become entrenched. Yes, there are some who won't work, just as there are some who don't pay tax, and some who steal from their families or whatever. But does it really matter if one of a small minority benefits from your (generic) generosity? You'll never know who gets the biscuits or tins you give to the foodbank, or who buys the old clothes you give to Oxfam. And if someone who does work and might have a better salary than you buys your dress, so what? The money has gone to the cause, and the people who do need to shop as cheaply as possible won't feel stigmatised if the shops are used by everyone in a community. The better-off buyer may very well donate a lot of things herself anyway.