Personally, if someone loves something I made that much, I'll give them the recipe.
Like other people have said, more often than not it is about taste and technique rather than an exact recipe, especially regarding savoury dishes (I only ever give a basic list of ingredients and method anyway), but when it comes down to a really good patisserie item, the recipe is definitely as important as the technique.
Example: after cooking professionally for over a decade, I only recently came across what I consider to be the ultimate chocolate cake recipe (see my blog: www.kiwisizzler.wordpress.com
). I've shared this recipe with loads of people.
Strangely though, as I enjoy photography, when someone recently asked me to email them the full-sized digital versions of some of my photos, I found myself very reluctant to oblige, and this person is an old friend. Maybe it is because it is a personal thing as opposed to something I got from someone else? I anticipate maybe making money from my photos one day and even though I already make money from being a good cook, which is basically the same thing, I am happy to share recipes.
In hindsight, I have been very lucky to have worked with chefs who have been happy to share a great recipe with me, so maybe this has instilled in me a similar response when I am asked.