My own experience is that even the smallest Linode VPS, with an out-of-the-box WordPress install, serving a blog live from the database without a cache plugin, can handle all the traffic HN throws at even a #1 story on a work day afternoon. All it takes is setting the Apache config such that it won't spawn more processes than there's memory available, or using something lighter weight than Apache in the first place.
I know this is a foolish connection to make, that their ability to keep a blog online isn't connected to the things that will actually determine whether the business succeeds or fails, but I can't avoid thinking it nonetheless.
To turn this rant into something possibly useful, maybe some advice: it's important to figure out the basics of setting up a web server, not because it's a terrible thing for your blog to go down, but because you're losing out on all the prospective users/customers that come with being linked to and discussed on HN or other sites. Even if they can read a cached blog post, you're probably less likely to get them to go visit the startup you're blogging about during this short moment you have their attention.