FireNetworkBlog: no 'real' PR5 or higher will have a domain authority of under 35 - 40. If it has, it's likely to be 'unnatural' as easy as that.
Telling people that DA isn't important it's nothing but bullshit. A decent DA high PR backlinks is always legit and helps way more than this bullshit PR8 domains. The SEOmoz data displays aren't up to date but give you a perfect idea of the 'history' of a domain.
'Real' PR has 'high' DA. If a domain is 'too fresh' to have some DA but high PR, I'd stay away. As easy as that. Bottom Line for me.
PS: If you think you can fake domain authority by massspamming the domain it says it all about your judgement when it comes to domains... Despite that, you're mixing up Domain Authority and Page Authority. PA isn't nearly worth as much as DA - that's why DA is one of the most important factors for domains & blogrolls.