It's easy. Easy, easy, easy. Register a new domain, add it to your hosting account, install some CMS. No problem. One provider, one invoice, and the auto-install robot will do most of the work. Want a second domain? No problem. Repeat the process and even add a new IP address if you want. All in one place, as many domains as you want. Comparable price, speed, and reliability to other hosts, but you can get a really good deal on the first year or get an expensive account upgrade for free with a promo code.
Ok, eventually you'll test the limits of shared hosting. I found it after about three bookmarking sites with SQL databases bigger than 500MB - running on a version of the CMS software that was notorious for using too many resources on queries to large databases. So, maybe you want to upgrade to a VPS, but you don't want to pick up half a dozen sites and migrate them to a new server. No problem! With a few clicks, I had all my domains migrated to a VPS and I haven't really noticed any outages or slowdowns lately. Again, comparable service and price to other VPS providers but I was able to build the account up organically from a smaller start. The VPS is also a LOT more user-friendly than the one you'd get at Linode or some place like that, where you'd have to install all of Linux, Apache, MYSQL, and PHP before your server can host anything.