bandwidth/resources control for "ProSites" & "WHMCS MU Provisioning"

Hi,

How does EduBlogs and wordpress.com etc. or any ProSites WP multisite control bandwidth, ram, cpu etc. resources for each individual site ?

what if some clown decides to use "Chat" plugin together with "Forum" etc. and basically run a mock on the hosted server and spoil the party for all the other sites ?

I know "ProSites" can control storage and "WHMCS MU Provisioning" basically the same.

- So i was thinking that WHMCS can basically sell a package/service that Plesk or WHM would create which would include bandwidth and other fine details.
Therefore can this WHMCS product be used with ProSites to control resources per site and therefore have different levels of bandwidth/resources for different ProSites plans ?

eg.
ProSites basic plan with limited themes/plugins/bandwidth/
ProSites Pro plan with extended themes/plugins/greater bandwidth/mail accounts/greater php memory limit etc.

Another scenario :
for a simpler setup without plesk/whm and just using a basic cloud server,
such bandwidth and other resources would have to be "soft" limits and noted in the sites policy in case of abuse ?

again, how does EduBlogs handle this ?
or is storage basically the main factor and everything else left unlimited ?
these days with cloud servers it seems to me that storage is getting cheaper but you pay basically for more powerful instances/virtual machines etc.

would love to hear anyones thoughts and opinions on this !!!

kind regards,

RC.