Yes, I was only describing the procedure in Terminal 1 for flights on UA.

No, I have never been asked for a boarding pass. I do this 5 or 8 times a year, most recently June 6, 2007.

Yes, I have seen people stopped to produced items. The most memorable was when a whole Tokyo tour(all wore the same jackets with insignias) group was asked to produce any and all Vuitton. Something like 35 people were taken aside, one at a time, to show items. I suspect they were looking for copies, but none of the people in my part of the line were close enough to hear what was going on. I was especially surprised, since tours usually get VIP treatment, with the guide turning in all the forms at once, with minimal inspection.

I have, however, been offered recipes for cannele by one official, asked to specify more completely the items involved several times when the bill just shows a lump sum amount, etc. The process can take anywhere from 5 minutes to an hour, astonishing since I almost always take the same flight at the same time outbound from CDG. I guess it depends on the random shopping habits of others.

As for fees on the detaxe, one shop I frequent deducts 5-7 euros, and several others refund the entire amount. I would assume you could ask in advance for the amount of the handling charge. Otherwise, just check the form:it always shows the amount of TVA charged and the amount to be refunded. The one time that I discovered I hadn't been credited the refund after several months, I took a copy of the detaxe form back to the shop, and they credited my credit card account within days. I know this presumes repeated purchases from the the same vendor, but I've had very good luck with the detaxe and refunds.