It could be a development version as well, they've hosted their blog on [corrected from comment below]Blogger for as long as I can remember...
[Google] http://blog.twitter.com/ -> http://whois.domaintools.com/74.125.113.121
[NTT/Verio] http://search.twitter.com -> http://whois.domaintools.com/168.143.162.123
[NTT/Verio] http://twitter.com -> http://whois.domaintools.com/128.121.146.228