Here's the thing about tithing, though, especially in a secular age...surely the idea is to give thanks for current abundance. Tithing is seed money for future prosperity based on appreciation of what has been received already. So isn't there an argument to be made for separating it from Scripture entirely? Everyone has a source of spiritual sustenance, even if they don't classify it as spiritual, and tithing to the source of that would be just as good as giving offerings from a harvest, for instance - no?
There's a podcast I heard about this, which is basically saying the same thing, and it makes sense.
Episode 10 is all about tithing and being 'christlike' in one's giving. The argument goes that we should focus on the giving for giving's sake, because that's what God wants, and let him take care of the mechanics of it all. I tend to agree with that.