Just make sure you walk away graciously and make it clear you'll still be there when you're needed. Keep sending them your newsletter or other promo material with details of your latest features, case studies of other satisfied customers, testimonials, etc. If these people are digging a hole for themselves, make sure you're the guy who has the rope ready when it starts filling with water ;) These guys could end up being one of your most loyal customers ever, if you save their asses later. Good luck.