Few days ago a friend of mine told be Hostgator has shutdown his website due to high resource usage. He is pissed and think it's totally unfair. I tried to explain him the situation but he wouldn't listen. He is planing to move somewhere else but to another shared account. He is going to learn it hard way that his problem won't be solve by another reseller or shared hosting account. He was using the $50 per month Hosgator sliver reseller package. For same price he can find a good VPS package.
There are very good VPS hosting providers who offer you great deals for $50 or even less. You can find a good VPS package with cPanel for $20 or upword. I'm talking about a good manage VPS with very good speed and uptime. I already have 2 VPS one which I pay $22 and other I pay $40 both work great with over 99% uptime. Also I do have a un-manage VPS which I pay $10 but has a good uptime.
So I don't see why you need to use a reseller account unless you want to sell hosting because If you use VPS you need to pay for billing software too. Otherwise for your own sites a good managed VPS is best choice for sites with high traffic. Also if you have social bookmarking sites, TopSite Lists, Web directories then you should use a separate shared account for these because these can become reason for your hosting provider shutting down your web sites. When several people using automated software to submit sites to you bookmarking or any site like that your can be sure it can end up in huge problems.
Wordpress plugins can do this too if these plugins are badly written. Always check reviews at Wordpress official site before downloading a plugin. Because this kind of bad plugin can give you serious problems. Same about highly active forums. These can be used by many members in same instant so there can be way too many data base connected open which can become a problem to other users and at end provider would ask you to move to another host or upgrade.