<p>Are pipes considered dangerous to use in Windows, from a security standpoint?</p>

If you are concerned about network sniffing, I suppose they could be since I don't think that pipes between systems are encrypted.  I don't know exactly how they are implemented in Windows, but I would expect that pipes between processes/threads on the same machine would be implemented with shared memory and not let traffic leak outside the box.  If you need secure communication between systems, I'd go with secure sockets.