usability of web services

hi ppl, im facing a design problem im hoping some experts here on the forum can help me out with. i have some experience with webservices but cant make up my mind on this one. my company is in the design stage of building a new appointment scheduling product. later on this will be part of a larger suite of products. currently, for just the scheduling part of the application, someone in the team came up with the idea of making all the server end web services based. the target deployment would be an intranet lan with one server and multiple clients connections using a client program (not via the web/browser) the fat client would use the web methods to retrieve all the required data from the database such as patient information, appointment availability etc. thus we would have quite a lot of web methods serving up this information to multiple clients. the reason my team-members are in favour of this architecture is because security of packets and firewall problems are a non-issue because of the very nature of web services. they say that using authentication, they can lock down the clients connecting to the server end the reason i do not like the idea of having all the web methods is because anyone can point a wsdl tool and build a client. also, the way i understand web methods is that they are well suited for public information (example: a stock quote), but in this case the data is VERY private and any breach could lead to major legal issues. please advice, thanx in advance