I haven't done a blog tour, so I've not used a company that organises them. I have been soured on the idea of publicists by being on the receiving end of some. I used to do reviews on my blog, and I got spam review requests from publicists asking me to review their client's books. Unfortunately, they didn't actually read my review policy, they just added my email address to their list and spammed me.
So, the only advice I can really offer is, be careful that you don't hire someone that will spam loads of bloggers on your behalf
