Depending on configure arguments libmp3lame may be built only as a shared library. But lame frntends link command using this library has -static.
Such clash may cause ugly libtool behavior.
In context of lame, linking should probably respect configure flags and link frontend dynamically if shared linking is enabled.
As a consequence of bug in libtool, this combination with --disable-static may create incorrect binary. For more see: http://lists.gnu.org/archive/html/bug-libtool/2009-11/msg00004.html