Who's an angel?

Well, certainly not me!
And, those who know me will certainly agree. Although, my DH has been known to call me angel on certain occasions (ahem).
Yarn Angel Knits came about because I used to be a first grade teacher. Thus, I had almost daily exposure to the Tooth Fairy and her exploits as related by my students. Wouldn't it be nirvana if there was a mystical creature who magically delivered the yarn of my dreams? Wouldn't it be delightful to wake in the morning and find the yarn I'd been drooling over had appeared under my pillow (or even under the bed - in case of large quantities) during the night?
But, what would be the trigger for the Yarn Angel's visits? Certainly not lost teeth! FO's? No, no, no! That would limit knitters to one, one (!) WIP and that would never do.
A new pattern design? Weelll - but how would I/we (after all, it wouldn't do to keep her to myself) swatch without the yarn in hand?
How about need? As in, I need such and such yarn. You know - all those yarns we drool over on other people's blogs, at all those websites we have saved in your favorites, we just had to pet at the LYS when we just had to drop in to check out the buttons? You know, the yarn that we just need - even if we don't yet know what we need it for?
Hold on just a minute here.
But I 'need' quite a bit of yarn every day. If 'need' triggered magical deliveries in the night, I'd soon be drowning in yarn. DH would have even less room for his stuff than he does now. Things just might get sticky on the home front.
So, what about it?
When do you think the Yarn Angel should visit?