The feeding guide that came with my new feeders states that whole bacon shouldn't be given to wild birds - presumably the salt content of a whole slice of bacon would be fatal... but a little bit of rind occasionally is OK. It also advises against peanuts unless they're from a reliable source (some nasty fungus can infect it and kill the birds) and in a small mesh cage or net so they aren't taken whole and thus choke smaller birds.

LTS