Legend/experience once had it that "aged domains" might either have a slightly higher "trust factor" than new (unproven) ones and/or that older domains might "get out of the sandbox" sooner than new ones.
I wouldn't add much weight to my domain choice/overhead for age, alone. Once any ranking factor gets a certain amount of attention for being an "easy way to rank" you can be certain that such factor is already being - or has alrady been - dialed down.
I would never actively pursue an older domain unless it's a particular name that you want which is taken - sadly this is mostly the case these days.
I've actually found purchasing domains from people often gives them an auto pentalty at times as once the domain's owner has changed, the credibilty and trust that comes with it was usually down to a decent webmaster.
So you have to be careful, it's very hit or miss, don't spend big money unless you've done this before...
Hm, seen the opposite. Registered a free domain, later I realised it had been used many years ago for some dodgy business - probably "adult industries" in one of its manifold expressions. Google did not index the site for months and only started doing so after many interventions from me via e-mail.
Aged domains can save you months of hard work, giving you a foot up in your niche. You can gain leverage with aged domains as Google gives more confidence in older sites, some can be purchased through <sites that sell aged domains>.
[edited by: Webwork at 3:13 pm (utc) on Feb 8, 2013] [edit reason] Self promotion is prohibited and repeated acts result in bannings and filtering. [/edit]