Interesting recommendation to hire a PR firm. I guess if you have $17M in cash and an audience that still pays attention to traditional PR, that's a justifiable expense...
A good PR firm works to maintain a very personal and trusting relationship with major news outlets, including the popular blogs and web presences. While there are a lot of bad PR firms out there you should avoid, a good firm is extremely valuable and should be included in your marketing strategy once the product has shown life.
However, most likely your first year (or two) you'll be able to handle a fair amount of the basic PR work yourself. Here's a good blog post from Josh Dilworth who works with a lot of tech startups.
We just had a discussion on PR firms that pretty much settles it in my opinion (http://news.ycombinator.com/item?id=462493). How can I include it in this thread? Hyperlinks are just not as efficient as some cute Ajax inlining...
You don't need 17M in cash to use a PR firm.
If you haven't read it yet: http://www.paulgraham.com/submarine.html
Question remains how does one find a good PR firm, these days a bad(read overzealous) PR firm could do a quite a bit of damage.
The landlord of my old apartment in Palo Alto told me that some previous tenants had tried to pay their month's rent in equity, because they were broke. He turned them down and the company turned out to be very successful. I'm pretty sure he said it was one of the PayPal founders, but I don't remember.