Just read a great post by Fred Wilson where he displays some very telling numbers regarding the adoption of the Internet by the rest of the world. At Aria, we learned this lesson accidentally, a sort of happy accident. When we started the company our intent was to serve largely North American entities and their language, localization, currency and availability requirements.
This picture illustrates what happened to us just in the past 24 months. Because of the leverage of the Internet we ended up with clients around the globe. These clients quickly drove us to learn about global payment method adoption, inter/intra country privacy compliance and payment processors we would consider "non-standard" in North America.
Additionally, the complex integration challenges were largely unforeseen when we started Aria. For instance, our original system could handle taxation for relatively static tax rates but because of the global commerce our clients required us to determine the tax rate on software and services around the globe on a real time basis. We've also had to integrate call centers in India and Asia which provide support for our clients and their end users 24x7.
These requirements are driving us to become an always on utility. It's hard for us to have a maintenance outage even at 2am est on a Sunday since it's in the middle of Monday in Asia. My advice to software companies everywhere: read or reread "The World is Flat"!
We have over 1Million end users in 236 countries and territories. We even have end users with billing addresses in Antarctica!!