Judging from my atlas, Los Angeles would be horrible for Australia and Asia, it is on the opposite side of the map. (</sarcasm>).
In all seriousness, there is no ideal location for everyone on Earth, the Earth is round and one point is always going to be farthest away from another point. I guess the only thing you can bet on is that there are more people in the Northern hemisphere than the Southern hemisphere and Eastern hemisphere than the Western hemisphere. So if you're really trying for a global reach with the most population, Asia would be the best choice. However, it would not be ideal for Eastern US / Western Europe users so you really have to analyze your target market. Other than that, any big POP in the Northern hemisphere as drmike suggested above.
In all seriousness, there is no ideal location for everyone on Earth, the Earth is round and one point is always going to be farthest away from another point. I guess the only thing you can bet on is that there are more people in the Northern hemisphere than the Southern hemisphere and Eastern hemisphere than the Western hemisphere. So if you're really trying for a global reach with the most population, Asia would be the best choice. However, it would not be ideal for Eastern US / Western Europe users so you really have to analyze your target market. Other than that, any big POP in the Northern hemisphere as drmike suggested above.