A few weeks ago, I created a bit of a flutter in this space by stating that I didn’t think Groupon’s business model was all that robust for the long term. Just to prove that I’m not a complete Grinch when it comes to Internet-based business models, let’s put the same test to Angie’s List — a members-only business review site that (unlike Yelp and TripAdvisor) charges membership fees. While the community of subscribers is smaller than some of its review-website brethren, 820,000 people have subscribed.