I'm no expert on what may or may not cause memory leaks, but I've been told plugins are always prime suspects. So try to disable/uninstall those first.
This is certainly not the normal behavior and I don't see anything like that here. True, Lightroom's memory requirements do seem to increase with each version, and those requirements may well exceed 8GB. But that should be handled by disk swapping if you have less RAM installed. Here's a screenshot from an export operation, note the memory graph:
(the screenshot is about a year old, I'm not at that computer right now to make a new one)
I understand from other forum articles that there is an issue with having large numbers of plugins loaded. I only have the one plugin, "jf Zenfolio", which is necessary for my work.
The export itself doesn't seem to increase the memory usage. It seems to increase when many photos are altered. The larger the number of changes, the more memory it consumes.
Currently Lightroom is taking less than 4 Gbytes, but I just started it and haven't started editing photos yet. What I'm seeing is that after an hour or so of editing photos (maybe 30 or 40) I'll run out of memory.
Windows 7, with 8 GB installed (the max for this motherboard).