Answering my own question for anyone else having this issue. (using the search terms i thought of because they didn't bring up the answers for me).
Trying to install and run middleman following the getting started guide on their website with Mac OS X 10.9.2. When trying to run bundle install getting errors about openSSL and event machine.
Aparently this is caused by a mismatch in expected versions with something called Clang which is part of the Xcode tools for mac. The update to Xcode tools causes this to fail. Using the command:
ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future bundle install
seems to work to resolve this issue.