1. Projects are over-promising and under-delivering
2. Kickstarter isn't a store and was never meant to be one. People have turned it into one, leading to all sorts of issues, including point #1
I think when you are asking for examples of abuse you are thinking of the first point, but the 'no multiple products' rule addresses #2. You aren't buying a product, you are backing a project. If you want multiple lightbulbs, presumably you can purchase them after the project is funded.
In other words, I don't think the rule is to prevent abuse, it's to bring kickstarter back to its roots and remind people what kickstarter is all about. It may hurt some projects but hopefully it will revert kickstarter to its original niche where it was adding a lot of value.
Of course, since LIFX is planned as a networked bulb you can't actually get the full functionality of it if you just order one. Also, for some of the smaller Kickstarter hardware projects the creator actually has no intention of launching them as a commercial product at all - they're essentially group buys allowing hobbyists to offer something they've designed to other hobbyists for less than the cost of building it themselves.
