Since no-one has mentioned this yet, I will:
One of the largest contributors to the apparent surge in renunciations has been among US citizens living in Switzerland (source: http://www.bloomberg.com/news/2012-05-01/wealthy-americans-queue-to-give-up-passports-in-swiss-capital.html).
There was such a rush that the US embassy in Switzerland had to take on extra staff to process the renunciations. This appears to be because in the fallout from the scandals at UBS, one of Switzerland's biggest providers of personal banking services, various Swiss banks have re-evaluated their risk profiles of foreign-national personal banking customers. Due in part to FACTA, it would appear, they have decided that US citizens are a particularly high risk, and US citizens living in Switzerland have therefore found it more difficult to bank with domestic Swiss banks, some of whom are declining their custom.
According to Swiss government figures (cited in https://www.overseasvotefoundation.org/files/counting%20american%20civilians%20abroad.pdf), in 2008 there were around 17,000 US citizens living in Switzerland.
What this might suggest, in my analysis:
1. US citizens in Switzerland do not necessarily appear to object to paying US taxes, per se, but it would appear that they DO object to the fact that the US government's attempts to impose the FACTA regulations is making it harder for them to manage their finances, get mortgages and loans from Swiss banks, etc.
2. This has prompted a large number of US citizens living in Switzerland to renounce their American citizenship.
3. This is likely to be a temporary surge - during which those US citizens who were experiencing particular problems with Swiss banks queue up to renounce their citizenship.
4. Once this particularly Swiss phenomenon has run its course the rate of US citizens renouncing their citizenship may well return to a more stable level.
Hope that's of some interest.