Just be aware that a large HOSTS file will affect your system performance. How large an effect is dependent on how powerful your system is.
The HOSTS file is not indexed, so each domain lookup will cause the file to be scanned from the beginning of the file each time. This is a very inefficient method of blocking domains, not to mention resource intensive on some systems. You're basically asking your system to sift through potentially several MB's of data each time a URL is resolved...
HOSTS file sites generally state that if you do experience performance issues, disable your dnscache service. Of course, this is not a great idea because now your web browsing will be a tad slower because each URL will now require a DNS lookup instead of only requiring a lookup for unique URL's because you've just killed your local resolver list. This will likely not be a huge slowdown and depending on the performance of your DNS service, you may not even notice it. But again, this is a very inefficient thing to do.
I never recommend large HOSTS files as a method of domain blocking.