The web is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you might think it's a lot of work maintaining your website, but that's just peanuts to the whole web. (with profound apologies to Douglas Adams)
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And if you're wondering how you might use a group, how about:
We hope you enjoy Google Groups; we really enjoy working on it, and it's been very rewarding to see all the useful things you and so many others have done with it.