Quote - I agree, I have rendered the scenes that HowieFarkes has put together for Carrara and they are fairly complex with items.  There are some in his gallery that are pretty large.

His Gallery at cgsociety http://howiefarkes.cgsociety.org/gallery/
His Gallery on his own page http://howiefarkes.com/#_images/gallery/

This one was interesting
http://howiefarkes.cgsociety.org/gallery/559385/

100 instances of tree's with about 10,000 replications per instance

Yeah, but notice I haven't set up many of those scenes with GI or Skylight. I fake it with a dome of spot-lights. Iit's faster and often times looks better than using skylight (plus I don't usually have to worry about "memory allocation" errors). The larger you render with Skylight the more likely you are to have your render fail, but with a skydome of about 30 spot lights I've rendered images of 8000x4500 pixels without issue.

www.howiefarkes.com