I forsee my site getting large very quickly. we just hit our 100,000 post mark last week.. and right now, we're averaging around 1000 posts per day. All I know is I remember a few months ago when I read every single post on my site, and now, I take a few hours off and I'm already a few hundred posts behind, lol.
But I must say, our new dedicated (semi-dedicated really because I host a couple other small sites on it for a few people) handles the higher traffic effortlessly.
On our shared server we encountered a lot of slow periods when it was busy, but now it trucks right on through
