Is there any reason for not enabling this? some sort of possible security risk?

Seems like it saves a lot of negotiation overhead on each request

This is what I mean by "SSL resumption" I think it's what you're
talking about too.
http://rdist.root.org/2009/03/10/note-to-wordpress-on-ssl/



2009/5/29 Igor Sysoev <is@rambler-co.ru>:
> On Fri, May 29, 2009 at 04:09:23PM -0700, Michael Shadle wrote:
>
>> If so, is it enabled by default? How can I enable it?
>
> If you mean SSL session reusing, then
>
> ssl_session_cache  shared:SSL:10m;
>
> Default is "ssl_session_cache none".
>
>
> --
> Igor Sysoev
> http://sysoev.ru/en/
>
>