I've been to shops that have held signings, and others that seemed to barely acknowledge FCBD. The shop I was in today allowed patrons to select up to five books, and I've seen some limit people to as few as one. Some shops pull out long boxes from the back and have some substantial mark-downs, others have sales on some of their hard covers and TPBs. One shop I know of has brewed up a special FCBD ale for the past couple years!
How the free comics are handled varies from shop to shop too. Some set up a special table or rack with them. Others have them on the counter by the register. The shop I was in today had tables out, but you had to check in with the owner's wife by the door so she could verify that you only took five and/or hold on to your freebies if you wanted to still browse the rest of the store. (The register itself was about in the middle of the place.)
Almost all comic shops are run independently, and there aren't many "rules" around FCBD so it's hardly surprising that they all treat the event differently. And I suspect that, for most people, it's not an issue because they only ever visit their one local shop, and don't make a point of checking out an array of different shops over a period of several years. You learn the way your local shop handles FCBD once, and then you just apply the same guidelines year after year.
But here's my thought, from a business perspective. FCBD has been generally considered a success for about a decade now. And the shops that go out of their way to make it a captial-E Event continue to do so year after year. Now, I obviously don't have access to their financial information, but it seems to me that if it weren't financially lucrative to have signings and brew/bottle a special beverage and hand out free hard covers to the first 150 attendees and whatever else they do, wouldn't they stop doing it> I mean, yeah, the special FCBD cake that you had made up and serve to customers for free is a loss in and of itself, but isn't that made up for by the additional sales you generate during the day? Doesn't the extra effort put into FCBD generate more income even after giving away comics for free? As a shop owner, wouldn't you stop putting a lot of time, money and resources into FCBD if you didn't gain anything out of it?
So why do some shops still just do almost nothing on FCBD besides having a few of the free comics available? It's not like we don't have plenty of examples of how making it an Event generates interest and revenue. Why would a shop owner continue to be resistant to that?