[chrisblair]

Thanks again for helpful comments that make me think.
Aim is to have a reliable system of 2 iphones and 2 Macs running OF and ICal where changes in one system are synced up with all the other systems. No need for private projects or other worlds.
I contemplated running the one MobileMe account but was concerned (as you pointed out) that collisions and conflicts may occur.
I took on board your "neutral country" comment in thinking about possible strategies.
The Con of this proposed strategy is the cost of the extra MobileMe account for the second iPhone, which IMHO is still very good value.
The Pro is the reliability and the ease of trouble shooting any glitches as the sync processes are broken into discrete steps, rather than all being melded into one MobileMe update. Still learning lots about how MobileMe works - esp in how to trigger an iCal update from the iPhone.

Working with single use apps to use with multiple users is a good mental workout - my history is that I started with maths at University in 1964, then Basic on an Apple II in 1980 with BPI software. Then dBaseII in 1983, then dBaseIII and then multiuser Clipper - the Clipper stuff started with S87 and some programs are still in use 20 years later - thunking in a DOS box in W2003 Terminal Server. BTW the acronym OF for me is apt in other contexts also :-) So am on a pretty steep learning curve.