Hi!
Obviously, dot infos are going cheap because nobody's buying them. Reasons why they're not popular may include:
1. Technical difficulties in accessing 4-letter TLDs (but I can't verify this as .mobis are selling at a premium);
2. People are used to .net, .com, and .org and they don't naturally put .info as a prefix when they go and surf a site.
But since people are using SEs in finding information anyway, I think it doesn't matter if we have a .info. I have 3.
