My very recent move to a dedicated server was a decision based upon a few factors.
1. My host decided a few months ago that it was no longer going to host adult content because someone loaded cp on one of their virtual accounts. I had to reassure them that I only deal with legal adult content and I gave them a whole lecture on 2257. They told me I was safe with them, but what if someone gets a hair up their ass one day and decides to void that agreement and shut me down? I'd be screwed.
2. I felt a desperate need to start moving myself to the next level and realized I couldn't do it with the bandwidth and resource restrictions on my hosting account.
3. I was damn tired of the four million other sites on the host's server slowing my sites down. Even if I was to purchase a larger account for space and bw reasons, there'd still be hordes of other schucks consuming server resources.
4. The wife said, 'start making more money or get a job.'
I've been at this too long, enjoying it too much, and I'm finally making money. In other words, I'm beyond the point of no return.