How important is a reliable web host? Well, very. If you are running any type of website, obviously the most important thing is to keep the website up at all times, or at least as much as possible.
At this day and age, web hosts are a dime a dozen. There are literally hundreds of them out there and it is difficult to find a good web hosting company. I'll admit that I am no expert when it comes to web hosts but I will give you a piece of advice. Do not be cheap when when choosing your web host. If you have the money to spend, spend it. Do not be stingy especially if you are serving potentially viral content. Once people start spreading links to your website on Facebook and Twitter, the traffic will flood in. There is nothing worse than your website crashing when people are pouring in.
This is even more important if you are trying to make money off of your content. If your website crashes while your content is viral, you are literally losing money as the clock ticks because the Internet does not sleep.
If you are unsure of your host, do not hesitate to ask around and read. It's good if you have friends who are webmasters whom you can ask. Do not rely on just one person or just one resource.
Choosing a web host is not like buying a shirt where if you decide you don't like it after you buy it, you can either return it, give it away or just keep it in the closet. As I have said, if your website crashes, you might be losing money. And even if you are not making money out of your site, it's bad branding for you when people visit your website and see errors. Even if you choose to change web hosts, moving from one host to another is not easy and things can easily go wrong so it's best to get off on the right foot.
Again, choose the best web host you can afford. Good luck!