UK: Why are Americans giving up their citizenship?

........but perhaps if they collected info when people relinquished it as to reason  it would be better.

There's a bit of a Catch 22 with renouncing. If an individual comments during the process that they are renouncing due to the complexity of keeping up with taxes, they're for the high jump. It automatically triggers an IRS audit. Therefore, no one says anything.

The staff(s) at the consulates/embassies know why people are renouncing, and from all accounts given by those who have gone through the process, it's a bit of a 'wink, wink, nod, nod, we won't ask'.

"Long term residents" refer to those with green cards who have held them for more than 7(?) years and give them back (you're required to file a form with the IRS if that is the case) so it comes under a different heading than renouncing. Also, remember renouncing is different from relinquishing. Again, two separate headings.

Again, don't get too hung up on the numbers.

The Ambassador to Switzerland made the following comment (and I forget whether it was for 2011 or 2012): the raw number of renunciations (and only renunciations) for the Bern consulate alone for the first 6 months of that year equalled more than 50% of the total number of renunciations, relinquishments, and green card hand backs 'officially' published in the Federal Register for the whole year. It makes the official numbers highly suspect.

For some reason, South Korea records the number of its citizens who have US green cards, and records when they give them back. Again for one of those years, the number of green cards returned in South Korea alone to the US was higher than the official number of renunciations, relinquishments, and green cards from around the world published in the Federal Register for that year.

The Department of State has confirmed that a number of additional staff has been enlisted for many US Embassies and consulates, just to handle the increase in renunciations and relinquishments. Waiting times went down from over a year in some consulates, and the process itself has been shortened (from the consulate point of view). For example, many now only have one face to face interview instead of two, again to reduce the backlog.