I just spoke to my accountant (who is also a lawyer) yesterday, and she said there's no point in starting an LLC unless you're expecting someone to sue you. I.E. you wrote a slanderous book about someone, or you're making outrageous claims for your products, or your products could be dangerous.
But, that's *just her advice* and I don't expect everyone to take it :P I might not even take it! I personally think it's a good idea to separate your personal finances from your business if you can, so *forming an LLC makes sense to me*.
Anyway, there are other companies who will do this for you, and as mentioned above, some states/localities make filing much cheaper and easier. Santa Monica offers an online DBA filing for around $30 as opposed to $100 or so for Legal Zoom, for example.
And, you can actually file the paperwork yourself if you're willing to go through the process and find out what you need (though, that's a big pain in my opinion).
For what it's worth, my husband did form an LLC with Legal Zoom this year, and he's been happy with their service so far.
Good Luck! And let us know how it goes :)