You've created a conflict among the placeholders. Both bind and lambda::bind 
declare _1. bind declares its placeholders at global scope, but lambda 
includes in the lambda namespace.

My using the inner namespace shouldn't include the outer namespace unless somewhere in the lambda namespace there's a using ::boost. I would consider that to be namespacing bug. For example using boost::lambda shouldn't put shared_ptr in scope either.

Consider the following example code:
namespace Boost{
    typedef char _1;
    namespace Lambda{
        typedef int _1;
        //using namespace ::Boost; //very naught. don't do this!!!
    }
}

void foo(){
    using namespace Boost::Lambda;
    _1 i; //fine as long as the using line above is commented out
}

Somewhere in the boost::lambda namespace there is a using namespace boost. I can't find it though.

There has been talk about merging these, but I'm not sure the status is. Of course, with bind becoming part of the standard that may be difficult.

-- Bill --

Thanks Bill. Maybe lambda can use the same placeholders as the standard. After all the placeholders are just zero sized tags. As soon as meta functions are standardized that work on them lambda could probably use them.

Chris