Can Web Services pass binary data efficiently?

To some extent Yes, actually Web Services are based on XML, and thus the emphasis is maybemore on textual data. we can add binary data as CDATA sections in yourXML documents you are sending.
However, probably a better way is to addbinary data as MIME-encoded attachments to your SOAP calls (see the proposedSOAP Messages With Attachments standard at www.w3.org/TR/SOAP-attachments).