protobuf 2.5 is a bit faster with a new Parse to avoid a builder step and a few other goodies that we'd like to take advantage of over in hbase especially now we are all pb all the time. Unfortunately the protoc generated files are no longer compatible w/ 2.4.1 generated files. Hadoop uses 2.4.1 pb. This latter fact makes it so we cannot upgrade until hadoop does.
This issue suggests hadoop2 move to protobuf 2.5.
I can do the patch no prob. if there is interest.
(When we upgraded our build broke with complaints like the below:
More over in
HBASE-8165 if interested.