Recently i've been working with Moodle 2 and benchmarking it with APC and Memcached installed. I ran into issues when testing Memcached..
My Memcache was not being populated by Moodle, and it appears that in the refactoring from 1.9.x to 2.0 that at least Memcache support hasn't been re-added. It's possible I have misunderstood how it has been re-implemented however, but I have been through the Oracle libraries in 2.0 and can't see where it would be. A grep of the code tree looking for $MCACHE turns up nothing in moodle/lib, either.
So.. has it been left out? Intentionally or has it just not been implemented yet?
I'm a PHP developer; if it hasn't been done yet and needs someone to take it on, I could be interested in doing it as I believe it could be useful.
Yes, you are right - memory caching is not yet implemented in 2.0. Memory caching was meant as a short term workaround for bad coding style. Ideally we should fix all those repeated queries and implement new types of advanced caching.
Thanks Petr. Does that mean that we should not use Memcached with Moodle?
It means Moodle 2.0 is not finished yet 
Is there plans to re-implement Memcached in Moodle 2.0? I had a look at the roadmap and in the Tracker and couldn't see any plans for it.
I'm currently writing documentation for our Moodle deployment and would like to have an idea weather I should expect it to arrive at some point in the future, however I understand providing an answer could be nigh on impossible given things are likely to change in the future anyway..
I'm currently writing documentation for our Moodle deployment and would like to have an idea weather I should expect it to arrive at some point in the future, however I understand providing an answer could be nigh on impossible given things are likely to change in the future anyway..