I've tried the google api (using nsjava), and it works well for searching, and something similiar could be added to openacs. In addition, web services could be used for the following items: importing/exporting/xfering content items, ecommerce payment gateways and inventory control, channels to other sites for education and intranet integration with portal sites, interfaces for single sign-on control for a group of sites on a campus or within a company intranet. That's just a few ideas, and I don't think there is any shortage of applications for web-services within openacs.
Simon, who are these people that are deciding what's important within the openacs community? It seems to me that adding support for web-services is as important as anything else that could or is being done currently.