I have long wondered about my native tongue's mysterious homogeneity. 90% of the time it's completely impossible to tell a Russian's home town by his speech. Siberians talk exactly like St. Petersburgers who talk exactly like Moscovites, etc. There are two very provincial non-standard accents, but they're dying. This is pretty bizarre. Of all the large European languages Polish comes closest to this level of homogeneity, but unlike Russia Poland is a relatively small, compact country.
How did this situation come about? I've had a chance to ask a couple of professional linguists this question and they didn't have a clue. Some will tell you that this homogeneity was created by the strictness of the Soviet educational system, but they're most likely wrong. Early Communism had a much harsher impact on Ukraine than on Russia and Ukrainian is as heterogeneous linguistically as Russian is homogeneous. In fact a large part of Ukraine forms a dialect continuum from Russian to Polish with pronunciation and vocabulary typically changing every few miles as you go from east to west and from south to north.
Normally languages that have appeared in their current homes recently are more homogeneous than languages that have been developing in the same place forever. This is why North America hosts fewer English accents than England does. But Russian spread across the European part of the modern Russian Federation roughly 1,000 years ago, so this shouldn't be an issue either.
If anybody out there has any ideas on this, I'd love to hear them.