There may be nothing inherently "wrong" with alternative roots. ICANN has never said that there is nothing wrong with alternative root TLD's. To the contrary they have said quite the opposite.
Here is a link to ICANN and their discussions involving alternative root DNS:
http://www.icann.org/stockholm/unique-root-draft.htm
One interesting quote from the obove link:
"One corollary is that with current architectures and under current policy, ICANN cannot support the concept of multiple roots except within an experimental framework, where experimentation is carefully defined."
I believe they are a bad idea from both a technical and a consumer point of view. Here are some reasons:
1) There needs to be a central controlling entity of allowed TLD's for obvious reasons. There cannot be conflicting TLD's and there has to be oversight.
2) Alternative root TLD operators can provide the same TLD's as other alternative root operators. For instance, dotworlds.net and adns.net both offer .USA domain names (among others) from competing alternative roots.
3) Consumers that are not tech savvy may not know the difference between an alternative root TLD and an ICANN sanctioned TLD. They will be unaware that their domain names are unresolvable for a vast majority of Internet users.
4) Alternative root TLD's do not have to follow any rules or regulations put in place by the Internet governing bodies (this may be a good thing, but I doubt it).
5) DNS itself was designed to have only one root.
6) ICANN can sanction a TLD currently being used by an alternative root TLD provider, creating a conflict. For instance, .BIZ.
In my professional opinion, I believe that the only purpose an alternative root TLD can serve is as a novelty.
Here is some good information provided by, arguably, the largest alternative root operators:
http://www.adns.net/about_alternative_domains.html
Here are some google links so that others can research for themselves:
http://www.google.com/search?domain...cann.org&q=alternative+root&btnG.x=0&btnG.y=0
http://www.google.com/search?hl=en&ie=UTF-8&q=alternative+root++DNS&btnG=Google+Search
Perhaps IETF says it better than I:
"The Internet currently operates using a tree-structured name space known as the DNS.
Of necessity, such a name space must have a single, authoritative root. Moving to a model that
would not require such a single, authoritative root would require replacing the present,
working DNS with some other system.
Such a replacement would require the development of a new naming paradigm, as well as the
protocols and software to implement it. Developing and deploying such replacement protocols
would take years, and would have enormous potential for disruption of the Internet.
IETF does not see any technical benefit in such an effort."