It depends on the nature of the
blog. Suppose you have a
blog where you're chronicling your attempt to take $20 and build it up to $10,000 playing poker. That's a chronologically-significant type of content, so those monthly archive links would be useful for a visitor. A
blog about the history of the legality of online poker would also be useful to have in chronological order.
But most
blogs I've seen are really static websites in disguise. In those cases archives are useless.
Blogs are about a two things:
1. Initiating conversations with others. (That's why
blogs have a comments field. The reason
blogs are different from forums is because only the blogger(s) can initiate a thread.)
2. Doing something where chronology matters.
Blog posts are dated and in a certain order for a reason.
If you're not doing one of those 2 things (or both), then you'd probably be better off with a static site anyway.