Well, in the purest sense, an investment results in some kind of a return of your investment. With Kickstarter, you're not investing your money, because you're not seeking to have it returned in any quantifiable way. You do not get a share of the profits of the game once it is completed, either directly or indirectly through some kind of share system.
I do not think it's about "legitimacy", or lack thereof, either; anyone can invest in just about anything. Rip-off ponzi-style investment schemes have caused literally hundreds of millions of dollars in damages, and they appeared entirely legitimate. Kickstarter is a donation system, wherein the market forces of the platform have dictated that a successful video game Kickstarter campaign gives a copy of the finished game to the people who donated. There is no law requiring this, nor any requirement from Kickstarter themselves. It's simply what the market has dictated.
So, Kickstarter is a gamble, plain and simple. It's like giving money to someone you don't know; they might do something good with it, like use it to buy food, or they might do something bad with it, like use it to buy drugs. However, even within that context, it wouldn't be difficult to argue that Kickstarter campaigns promising a game to backers are entering into an agreement with said backers. Unlike a donation, wherein nothing is agreed to be supplied, these campaigns are stating in no uncertain terms that an end product will be provided. That's not an investment - its simply selling goods, even if they do not exist at the time. I suspect violating that agreement might fall under common retail law, or the digital equivalent should one exist in the countries in question, even if no contract has been signed. They sold something, and you paid for that something. At the very least, refunds would be issued in full.
There's just a simple disclaimer on the Kickstarter website, and that's about it. They get to keep their hands clean while raking in the commission.
I think "keep their hands clean" lends a bit of a "bad" slant to Kickstarter that isn't warranted, in my opinion. Kickstarter is a platform for people to use, and has successfully helped literally thousands of projects become reality. Asking Kickstarter to intervene, or expecting something more than an open platform, would alter the platform's success entirely. Legal contracts would need to be drawn up, reviewed, mailed out, signed, entered into and held. Of course, Lawyers would also need to be involved, and the barrier of entry in terms of sheer funding costs goes through the roof. Kickstarter would need more than the current ~5% to cover their costs, and backers would need to start included legal costs in their funding requirements.
I imagine something like XKCD's point wouldn't be too far off the mark:
Anyway, in my opinion the open platform has dangers, as we're currently seeing, but as long as people are informed of those dangers, it should remain open. It falls to the individual to make the decision, as it should. Abuse of the system can still be policed using the legal system; I'd argue that it wouldn't be difficult to take this person in question to court for a full refund of a given backer's pledge, and on top of that he would need to pay the legal costs. A two or three thousand backer class action would make it easy for international backers to be represented as well.
Personally, I don't think bringing in the shiny red-tape of "legitimacy" does anything to solve the problem of people abusing the system, and ultimately I fear it would simply damage the success of Kickstarter and what it's goals are. In the end, I guess its a trade off.
My two cents, of course.