I'm not sure if this topic deserves to be "relegated" to the lighter side. Surname distribution mapping can be a serious and exceptionally useful tool in braking down brick walls (the offering from Ancestry is, however, a bit light on its value)
In their Book The Surnames of Wales published in 1996 John and Sheila Rowland’s showed how, even in Wales, where the use of common surnames is much more prevalent than in other parts of the UK - about 60% of Welsh people use the top ten Welsh surnames in comparison to just 5% of English people using the top 10 English surnames - surname mapping using 2 surnames from the period 1813 to 1836 can pinpoint fairly accurately where a couple are likely to have hailed from. Even if it is a Jones marrying a Jones!
If such a tool were available for the whole of the UK it would be of tremendous value to family historians
Unfortunately the Rowlandses have never made the computer programme the used for their research or the databases that they fed into it publicly available.
The reason for using marriage data from 1813 to 1836 was because this was a period where surnames were fairly well established and railways hadn’t, yet, made mobility a huge problem.
As much of the marriage data for 1813-1836 is available from the LDS and or FHS's- if anybody knows how to create a web programme to filter the data, I'm sure that a very, very useful tool could be created.
