That's right. A problem we have doing the RNP (Radio Network Planning) for 3G networks, is that the cell capacity per user decreases with the number of users (they share a fixed bandwidth), but also the cell size become smaller as the number of users in the cell grows. In some cases we saw some zones lossing the signal (becoming black zones) when the number of users in a cell increases significantly.

This is why, in Europe when they have a special event like a football cup final, the operators install in the surroundings of the stadium temporary cells to cope with the increase traffic and the high number of users per cell.