Absolutely - I'm sure you've heard of the idea of technical debt [1,2] and sometimes it makes sense to build up technical debt to get a system off the ground, then worry about maintainability, documentation and whatnot in your copious free time later on.

[1] http://www.codinghorror.com/blog/2009/02/paying-down-your-te... [2] http://en.wikipedia.org/wiki/Technical_debt