Shared hosting or cheap VPS?

[ZiNgA BuRgA]

But how much are you paying for shared hosting anyway?  I see some hosts charge up to $10/mo, though most probably around the $3-5/mo mark.  You can get a decent VPS for that amount.

For start up forums, personally, if I didn't have existing servers, I'd go with free hosting and "free domain name".  Don't believe the bullshit that idiots on the MyBB community (most of whom can't run a decent forum themselves) spread about avoiding anything free; unless you're targeting webmasters, or you're trying to sell stuff, your visitors really won't give a damn about the hosting.  Though do take some time to ensure that the free host is reasonably reliable (it doesn't have to be exceptionally great, just reasonable most of the time).
I started out on free hosting using the free subdomain provided by the host.  Only moved to paid hosting after the board accumulated 10k posts, and only because I was exceeding the limits of free hosting.  If the forum had failed, I would've lost nothing but the time I invested.