Obligatory question: why would I use a shared memcache when having memcache on own server is as easy as sudo apt-get install memcache?
If this trial works, I can relatively say that we won't be talking about 200MB, but GB of "burstable" cache. And you won't get it for free on Linode.
Also, this is an experiment.
edit- Just realized you have to being using Linode as well. Now I question this too. I thought this was going to be Memcached as a service.
Hope I could answer your question..
The reason I was slightly interested is because Windows Azure right now doesn't have good support for any sort of distributed cache system. So we've been shopping around.
Memcache will only make sense if it is hosted in the private LAN.
I think the point is that he's only offering it to Linode users in the Dallas data center, which is where his service is located. Therefore the latency will be in the sub 1ms range, comparable to a private LAN. There may be other issues with this approach, but latency isn't one of them, at least in this implementation.