It can be effective if you manage to get hold of quality posters. It is good for getting a few threads and posts in a brand new forum and if you want to give your forum a fresh boost if it has been sitting idle for weeks or months.

If you are going to hire posters, be specific about what you require. Some don't care what is posted, as long as someone posts, but that isn't the right attitude if you want to have a decent memberbase in the future.

You have to have a decent budget to keep paying the posters for it to work.

I tend to agree with LPspider. As a forum reader, I look at half the posts on this site- "What you favorite comic", Do you wake up to your alarm", and dozens of other posts which have nothing to do with the site, and are barely legible. Then I wonder how much they are getting paid to post this stuff, when I can't get an answer to my web related question. All fluff and no stuff makes your forum suck.

So, I tried out WiredFlame; Their $20/50 post package.

I got 2 writers.
One writer was, not too bad. English was his first language, he just had zero knowledge specific to my forum's topic.
The other produced some of the most well thought out threads I've seen. If I could hire just that writer again, I would in a heartbeat.

Luck of the draw I guess.

Overall, I'd say if you're going to launch a forum and don't have a 'launch team', purchase a few posts from a forum boosting company, but don't rely on them.

Its hard to trust Inb0x when their website reads

All our writers has a history of posting large quality posts on a range of different forums for work or for a pastime.

before our writers have started there work

We are currently in discussions

That is just bad writing and "their" site is full of it. It is probably some kid who has the time of day to post on forums constantly...