I like to use a real estate analogy to explain website hosting. I lease a “building” from a big, well-known hosting provider. I sub-lease apartments (websites). I also live in the building and I am the building manager, the interior designer, the plumber, the doorman, and the janitor. If the plumbing goes out in apartment 42 (a website), I’ll instantly get an email about it and can fix it because I know exactly where the main water valve is in the basement. I know what’s going on and how to get it fixed. If I can’t get it fixed, I have a direct line to the building owner. That’s about it.
If you’re hosted at e.g. Yahoo, you’ll be going to them for any questions, but if you come to me while you’re hosted with Yahoo, you’ll need to give me the keys to your apartment, I’ll need to search around the basement, billing you for the time, and find the main water valve. Maybe it’s in the exact same spot as it is in our building, great, easy. Maybe it’s not and it’s going to take me an extra hour to fix it. See the comments below for more about the “big guys” as hosting companies.
The hosting building is going to have the same 99.9% uptime as all of the big guys–because it is one of the big guys. No, I don’t have a 24/7 help desk 800 number. But how often are things truly the fault of the host? Well, statistically, 0.01% of the time! The usual culprit is your ISP (SBC, Comcast, Earthlink, etc.) and your Internet connection. The other culprit is your own computer or network. In the three years I’ve been with this host, they’ve had two little glitches and they were fixed before I could even email them about it.