Have you ever seen or purchased a limited-edition book that came already signed by the author or contributors? Yeah, it's pretty neat getting a book like that, and collectors are willing to pay quite a bit extra for a book signed by a famous writer.
Some people think that the publisher rounds up all the authors for a wine and cheese party at which everybody signs the books, but that's not usually what happens. Trying to get a bunch of writers together in the same room at the same time is like herding cats, and mailing boxes of books around the world is terribly costly.
So, what publishers do is mail around stacks of pages -- signature sheets -- that the authors then sign and ship to the next people on the list. After the sheets are filled with signatures, they're added to the rest of the book's pages and bound into (or simply tipped into) the finished book.
If you aspire to be an anthology editor, be aware that signature sheets -- while they are indeed a cool thing to do for a limited edition -- are often a big huge expensive pain. This is particularly true if there are more than 10 authors involved and they're not local (if they are local, you can attempt to host the aforementioned sheet-signing party and get it done fairly painlessly).
If there are more than 20 authors from all over the country involved in your project and you've got to get everyone's signatures on the sheets, it's just like Disneyworld, if Disneyworld involved sitting in a hardbacked chair for 10 or 12 hours only to have circus midgets rush out of a closet and pelt you with dead fish at the end of your wait.
Things that will likely happen to signature sheets:
- The post office will go "OMG! Big box = teh bomb!" and haphazardly slash it open with a boxcutter and consequently slice or otherwise munge up the top and bottom sheets in the process. *
- At least one author will have carpal tunnel syndrome and not be able to sign the sheets for months and months.
- While the author is recovering, one of the author's cats will climb to the top shelf where the signature sheet box has been put for safekeeping, and thoughtfully hork a big wet hairball therein.
- While the author was recovering, postal rates went up, thus rendering the postage you included in the box insufficient. Author is dead broke due to having to pay the doctor for carpal tunnel surgery. You will have to overnight a money order to the author to enable her to send the box along to the next author.
- Next author in line finally receives the box, then proceeds to pitch a fit because "there are way too many signature sheets" (you included 20% more in a futile attempt to compensate for boxcutters, hairballs, and coffee spills) and thus the publisher is trying to cheat him. So you have to call author up in an attempt to explain the presence of additional sheets to cover for loss, but he's not hearing any of it. Author holds entire box hostage until his wife counts up the sheets and tells him that you were right all along. He signs the sheets and sends them along without apology.
- Somewhere between Bloomington and Boise, the post office will lose the box entirely. *
Alternate Scenario: the box arrives safely in Boise, but the author's angry drunk spouse believes the box is from a lover, and throws it in the dumpster.
Alternate Alternate Scenario: the box arrives, but is stolen off the front porch by a creepy stalker who's been going through the author's mail; signatures of some authors will later show up on Ebay.
Son of the Return of the Alternate Scenario: After the box arrives, the author's town is hit by a flood, hurricane, tornado, volcano, alien invasion, or plague of paper-devouring locusts.
Regardless: you'll have to print up a whole new set, and reobtain the first bunch of signatures.
* Both of which can happen to book shipments, too. We recently got a box of chapbooks which had been obviously opened by/broke open at the Post Office, spilled onto the floor, possibly stepped on, and hastily dumped back in the box and resealed. Moral: use strong packing tape and plenty of bubble wrap.