That question came from my friend who decide to use paid hosting after get banned by free hosting provider.
My answer is : depend
If you have only one domain with huge traffic (term huge is more than 1k) then you’ll need to consider one account for one domain. But if you have around 100 uv / day for a domain then I suggest to host maximum 5 domain for one account.
Other factors need to concern are :
- Dynamic or static; dynamic type content like wordpress, joomla, drupal will consume more than static html.
- Number of process allowed; a few host will give you throttle that put your host in freeze mode. No more access to new visitor until big trafic go away.
- Cpu process; extensive resources also prohibited. Make sure to use minimum plugin and use 3rd party service like nrelate that store all related post of your blog on their server.
- Language version; people often unaware about php version they use on their shared hosting. Use newest but stable version like php 5.3.xxx
- CDN (content delivery network); use font from google, twitter bootstrap from cdn is faster then host it and serve it yourself.