I've occupied both sides of the pulpit, so I know some of the joys, and some of the down-sides, of each. I'll share two that are a little of both.
First: Preacher stories. Because a preacher should proclaim the word of truth (1 Timothy 2:15), and serve the God of truth (Isaiah 65:16), "preacher story" should mean "true story." But it doesn't, does it?
The story may not be a lie; it may be an exaggeration. Or it may not be an exaggeration; it just may be fuzzy. Or it may not be fuzzy -- it just may be forty-third generation hearsay.
Like the story about the famous evangelist who had the drunk tell him, "I'm one of your converts," to which he replied, "You must be. If you were one of the Lord's converts, you'd not be drunk." Who was that? Moody? Wesley? Billy Sunday? It is told of a great many preachers. What bothers me is that it doesn't bother some preachers whether they can source the story or not. It's told as true.
Or take a favorite story of mine: Athanasius, told that the whole (Arian-leaning) world was against him, and boldly replying, "Then Athanasius is against the world!" I love that story. It should be true. I want it to be true. But I wanted to know for sure, to source it, before I told it as true. So, for a time, I tried and tried to document that story. I never got further back than the Middle Ages. So I have to tell it with a proviso.
We should care. We should want our hearers to be able to take what we say as grounded, sourced, solid. We don't want them to feel that they have to look up everything we say on Snopes.
Which brings me, very similarly, to...
Second: Unsourced quotations. Two of the greatest offenders I can think of are William Barclay and Warren Wiersbe, to touch two very different theological camps. Barclay was famous for making quotations without citations; but Wiersbe is the same. I love reading his Walking with the Giants. It's a wonderful book. But the documentation is atrocious!
This is a book full of quotation after quotation, but almost none of them is sourced! Wiersbe does give a general bibliography, but he doesn't cite his specific sources for his specific quotations and stories, as a rule. I can't verify what he says, unless I have the leisure and desire to read every page of every book in his bibliography. If I were to quote any of them, I'd have to say, "Wiersbe says that Dale said...."
And yes, you now know something about me. My sermon note do have footnotes. I may be a bit of a nut about it. The dear lady who typed my Master's thesis complained good-naturedly that half of it was in the footnotes.
But it's a bit like the whole Santa thing. I never told my children that there really is a demigod-Santa Pelagius looming somewhere, judging their works. First, it isn't true. Second, I don't think lying to kids is very nice. But third, I don't want them to have to start filtering what I say, and wondering whether ol' Dad is having a bit of a snicker at their expense when he talks about this other invisible figure who sees them when they're sleeping, and knows when they're awake. (Santa? God?)
In the same way, I don't want folks who hear me preach have to wonder whether I checked out what I'm preaching for myself first, or whether I'm just weaving a yarn because it sounds good and makes my point well. And as a hearer of sermons, I don't want to have to wonder, either.
(BTW, to the best of my knowledge, my current pastor never does either. He's an atrociously well-read man, with a terrific memory.)