I rather liked James Wyatt's story about his son improvising. It showed he'd really sparked something in his son, something that will be a memory for both of them (James especially) for a very long time.
There's an even better and more appropriate example in that same section, about players asking if there's a Wizard's guild in town, and the opportunities it generates. By stopping for a second, thinking whether there's any harm in a Wizard Guild actually being available or not, and if no direct harm, allowing for it, you've just added something more three-dimensional to your game, you've added a place that players are interested in where there are NPCs, story hooks, and plenty of new ideas to inject. Remember it does say, "As often as possible", which means that it's not a "get out of jail free" card as some might interpret it.
What I do know is that one of the best Game Masters I've ever met uses the technique, and that's good enough for me.