I've been bitten by the lack of progress measurement and having "agile" requirements before. In most cases my physical presence is a crutch for a bad process, it allows people to make ad hoc decisions because they can grab me and talk in the hall for 10 minutes.

If people being physically present is no longer a given then some level of structure has to be put around decision making and disseminating the results of that to the rest of the company. Too many times I've lost days of work because X was changed to Y and I wasn't at my desk when people were herded together to make that decision.

Having people geographically distributed forces you to deal with communication up front. People are trained to use mailing lists, IM, bug trackers, commit messages etc. properly rather than assuming that if someone wants to know wtf just happened they can shout at you across a room. You hit problems like Mike being the only keeper of process Z early rather than on day 1 of Mike's 2 week vacation to somewhere with no cell reception...