Well, if any of you guys ever come to the uk, try a fell race... you will see many runners with fanny packs (we call them bum bags here, a fanny is something different). Snobbish about your running as you may be, I can guarantee there will be at least one (put possibly 20/30) guys with a fanny pack in front of you.
I use mine in training; I sometimes carry a camera in it; sometimes waterproofs, energy bars, a whistle, and occasionally a map and compass). Basically, they're the best way to carry what you need to make your running safe and enjoyable.
And I am sorry, if you are a first time 5K runner, and worried about dropping out, not having money on you, or you want a drink during your race, then by all means carry a fanny pack. If any snotty track runner makes a remark to you about it, advise them to broaden their horizons, & come and race abroad on the fells. They're in for a big ego bruise!