Databases are fine, but blogs change infrequently and mostly serve the same static content. Caching the database-generated pages, or just serving static files, if much more efficient, especially when a crowd comes.
Can better blogs be built on top of Google's App Engine? I've been building on top of it with Go but I don't use app engine's data store, and I'm not sure that I want to. My little database is a pregenerated Go variable.
You can run a blog on a cloud platform, set up auto-scaling, and withstand a reddit / hn / slashdot crowd.
You will likely run out of the free tier and into significant spending during the spike pretty soon.
If you ran a highly interactive page that required a lot of non-trivial server-side processing, I'd understand.
But blogs serve the same static content to almost every request. I don't see why burning a whole lot of CPU and IO on it by running python/php/ruby and hitting a database many times is worth it. Serving a set of static files automatically generated by a blog engine (like Jekyll) seems much more reasonable to me.
Regarding comments: Disqus or something like that could help. Or you could turn the comments off during a spike: seeing the content without comments is a much better user experience than seeing a 500 Server Error page.
