For many sites, daily backups wouldn't be a problem. However, for larger sites the bandwidth could be a significant problem. It would be possible to perform incremental backups, however, as a reseller it's unlikely that you would have access to shell and be able to add packages for that purpose.

Aren't resellers usually given jailed shell access? I think that's an essential feature of the package.

Some plans may include shell access, however, I do not believe it is include with the majority. Even with jailed shell access you wouldn't have permissions to install and customize packages (.rpm). It's possible that some hosts might install the packages for you and allow you to access the necessary files, however, I'd say that it's very unlikely. This is one reason why VPS's are becoming popular.

Agree on this, but reselling packages are here to stay, don't think that soon will be haveing everyone reselling from a vps plan.

Don't think so either. It's not always easy to choose and sometimes worth the risk, big companies or small ones. It's like, in the big ones you're just 'a' customor or a visitor... in the small ones they take better care, or at least try to have a better band.