Surely the background is somewhat stationary during, so there is ample space to refine that with less fast-moving data.

Sure, you have to get better hardware to properly capture the fast moving target of the photo, but it is not an either or question.

I think a lot depends on whether you stand to loose and the other bloke stands to gain from those lies - if these are old war stories that bear no relationship to my current life, well, that's just entertainment, whatever.

But if the other person is telling me "deposit money in this ATM, it's totally secure' then I'd be a bit assertive with holding him to account.