Plugins and MultiSite redundancy


I experiencing problems with MultiSite and towards the end of getting all plugins loaded onto a subdomain. Are there particular plugins such as security plugins that do not need to be loaded twice such as some of the security analysis plugins?

Is for example it necessary to have Google Analytics enabled for for each site? O.K. ... see.. I'm not crazy... I just was loading GA and it has a section to designate subdomains... is there any other information you have regarding this topic of redundancy and plugins? Thank you again... further...

A good example, is it necessary for Snapshot to be loaded on a subdomain? Or is one load on the primary all that is necessary to back up these sites since the info lies within tables and wp-content.

Same for WP-Database manager. Redundant?

I am having problems I think with Ultimate Branding again after the recent plugin upgrade. Hand in hand with the older version of bpmedia that was working again. Strange but not surprised. The Ultimate Branding was working for a few updates. Still not sure of causes but if I can get some general plugin insight starting with the questions above I believe I can solve it or help eliminate what is redundant or not necessary. Infomation please.