Ruby, a system similar to what you describe is already in place in the IT field. Essentially, in the computer world, you've got a few huge mega-companies that have provided learning courses that result in a certification. For example, Microsoft has an entire line of varied certifications in different fields...one could go through the required courses and take the requisite tests and eventually be declared a Microsoft Certified Applications Developer (MCAD). That would mean that you're able to work with and innovate using Microsoft's various application platforms.
The essential problem that accreditation solves is standardization. Employers don't have the time, nor the desire to have to research prospective employees' credentials. Take the point of view of a large company: dozens, if not hundreds of applications are submitted to major corporations on a daily basis. What kind of manpower would you need if you were to research every resume and every credential? Even if the applicants gave all sorts of information regarding themselves, who's going to read all of that? Plus, if you research one resume, you would need to research all of them...there's no nitpicking or nepotism possible. I realize that most large companies will do multiple interviews with a selection of candidates before making their choice, but that still doesn't alleviate the burden of having to swim through resumes to select those candidates. Yes, the interviews count for a good chunk of hiring process, but the resume is what gets the foot in the door.
Now look at a small company's point of view: You've got a web-design business, and are looking to expand...you need a new developer. You get 10 resumes in a week. 3 guys have standard degrees from accredited universities, 5 have relevant Microsoft certifications, 2 have some sort of other credential. If you can pick 3 people to give interviews to, who do you choose? Personally, I would pick the 2 guys with standard degrees with the most job experience, and 1 of the MS guys with the most impressive resume. I wouldn't even bother looking up the alernative credentials for the other guys. A small business owner simply cannot afford to waste his or her time doing background checks on obscure credentials.
In the end, the crux of the issue is standardization. While non-standard credentials are better than nothing, when you're in a job market competing with people with known, proven credentials, they're not going to help much, if at all. The Microsoft Certification, and other programs like it, are a partial solution to the issue, but it's not the end-all, be-all. The best solution to the issue is what we currently have...gov't accreditation. And yes, degrees from accredited schools are expensive, you end up with lots of debt afterwards, and they take a lot of time, plus a good amount of inconvenience, but in the end, you reap what you sow. It isn't exactly fair to have people studying at home, taking courses at a brisk, leisurely pace, paying chump change for their courses, and then have them be able to compete in the job market. It's simply Unamerican, and I'm not even that conservative.