Essentially everyone, when they first build a distributed application, makes the following eight assumptions. All prove to be false in the long run and all cause big trouble and painful learning experiences.
1. The network is reliable
2. Latency is zero
3. Bandwidth is infinite
4. The network is secure
5. Topology doesn't change
6. There is one administrator
7. Transport cost is zero
8. The network is homogeneous
ref:
http://en.wikipedia.org/wiki/Fallacies_of_Distributed_Computing
http://www.rgoarchitects.com/Files/fallacies.pdf
WebServices and Eight Fallacies -
http://www.oreillynet.com/xml/blog/2002/07/web_services_and_the_eight_fal.html
Distributed Computing Fallacy - http://feedblog.org/2007/09/23/distributed-computing-fallacy-9/