Most seasteaders would prefer to define their own sovereignty. And of course this has its issues with respect to being attacked by various folks, pirates, navies of various countries, etc. A fairly good writeup appeared in Ars Technica [1]. James Grimmalman, a professor of Law at New York Law School, did a legal analysis which was fairly widely cited as well.

[1] http://arstechnica.com/features/2008/06/seasteading-engineer...

[2] http://stevereads.com/papers_to_read/sealand_havenco_and_the...