Mmm. I have occasionally suspected people of deliberately saying yes and not doing it, on the (presumed) basis that it provokes less argument than saying no and not doing it.

In the case where I said yes, the favour being asked of me was something I was rather uncomfortable doing for personal reasons, and I was being asked it in front of a lot of people to whom I really didn't want to have to explain why I didn't want to do it. So I said yes, thinking that I would just grit my teeth and do it anyway, but at the same time sort-of-knowing that I might not.

Afterwards, I realised I didn't care enough aboout what the asker thought of me to make me actually grit my teeth and do it.

If it was just something like lending a book, and I didn't want to lend it, I would just say no!

That's a bit naughty and would annoy me.

(One of the people I've tended to suspect of it is our once-mutual landlord, actually. Though the circumstances didn't exactly match the ones in this poll...)