Some might say, hey, just use the year or the year and month! That's cool, go for it. I like that for the most part. Some people feel super strongly that having the date in the URL is vital since it gives people information about when the article was published. I don't feel that strongly. I think that information is vital but it's more important it's visible on the page itself. SEO expert (not kidding, he's the man)
Joost De Valk told me dates in the URL's can kill clickthrough rates on Search Engine Results Pages since the content can look old before they even see it.
Personally, I've opted to start my URL's with /%post_id%/ then also use /%postname%/. It looks a little weird maybe, but I don't overly mind it. Performance is more important to me.
What can WordPress (the project) do?
I'd vote that on the Settings page for permalinks, it should at least have a sentence like "It is not recommended that you begin your permalink structure with /%category%, %tag%, %postname%, or %author% for performance reasons."
What about me?! I use /%postname%/. What should I do?
The thing to consider is how many pages you have now, and how many pages you might ever have. If you are pretty sure you'll have very few, like under 20 pages EVER. Then whatever, I think you are probably fine with that structure. If you think you might have more than that, I think you ought to change now before it becomes a problem. Consider one of the date based structures or starting with the %post_id%.