Some food for thought...
The How To Demo page on the wiki (https://cwiki.apache.org/confluence/display/DRILL/Demo+HowTo) has Ubuntu use apt-get to install the protobuf, but if you are on 12.04 (LTS) this puts version 2.4.x on your machine.
That means you'll want to do the install by hand (the recommended install for CentOS/OEL/RHEL, etc). Following that install step gets the correct version, but on Ubuntu (12.04 again), you'll also want to run "ldconfig" ($ sudo ldconfig) right after installation. This is due to a stale ld.so.cache (sometimes the .so isn't found right after the install. See the comment thread here: https://code.google.com/p/protobuf/issues/detail?id=213).
In this ticket, the [ERROR] result of maven might have been something I ran across earlier, but we would want the debug output ($ mvn clean install -X) to see what the issue was. If it was a missing .so, but the right version was installed, and the user is on a ubuntu distro, running ldconfig might help.