Re: Recommended hosting service?
Media Temple are not bad , have one of their Dedicated virtual servers, possibly a bit pricier than the others, but excellent fast support, very good KB, good active forum, server performs well has plenty of bandwidth, memory and disk space, plesk panel plus licences not that I like control panels that much. Full SSH root access, do what you like with the server etc.
As for memory required to run something like WPMU and Buddypress it really all depends on how busy the site is we have on this particular server 1.5GB which is plenty. WP/BP should run fairly well in less, min I would want though is 512MB. More important I would have thought is having a full set of resources to dedicate to the site so wouldn’t consider running on any form of shared hosting only VPS or Dedicated especially when things start to get busy.
All of the hosts mentioned are good and all I think are recommended on wordpress.org so should be fairly safe whichever you choose.