Oni Press debuted Resurrection last week. I haven't picked it up yet, but I ran across an announcement online (though, curiously, not on Oni's web site) that they'll be running a letters column. While that's an unusual move in and of itself these days, they're additionally going to be sending a free copy of the next issue to every individual who gets their letter printed. Furthermore, the writer of the best letter in any given month will be sent an autographed copy of the issue #1 plus some original art by series artist, David Dumeer.
On the off chance that you're missing their point: it's a promotional tool to get people to buy the comic. It's a little unconventional in several ways, but Oni's somewhat unconventional as a publisher.
Obviously, it's far to early to even begin looking at what kind of sales volume we're realistically looking at with this title. ("Realistically" being something of a misnomer here anyway, since we'll only have estimates based on Diamond figures, at best.) But I think it's safe to assume that Resurrection won't break 10,000 issues this early on; I'd wager we're looking at somewhere around 5-6,000 for the first issue and just shy of 4,000 for subsequent issues.
Assuming a nice, round figure of 10 letters published per issue (I chose 10 largely because it makes my math easy and it's likely to at least be in the right ballpark) that would mean that .25% of the lay public* reading the issue on a regular basis get it for free in any given month. A $15 investment per issue (it certainly doesn't cost Oni a full $3.50 to produce each issue!) to sustain sales on a book that might generate $14,000 in revenue each month. Not increase sales, just sustain them.
But, you know, that strikes me as a pretty sound investment.
While it varies from industry to industry, there's a pretty good rule of thumb that it will cost you more to get a customer than it will to keep an existing one. To get a customer in the first place, you need to first attract their attention, then convince them to use your product/service. Once you've done that, all you need to do is make sure that it's easier/better for them to stay with you than move on to the next guy.
You ever listen to an editor from marvel or DC? One of their biggest complaints/frustrations is that they keep having to come up with new ways to make sure that people who are already buying their books don't stop. That's one of the reasons why they change creators out more frequently than they used to. There's a natural "bleed rate" at which readers will leave a title unless they come up with some incredibly compelling reason for them to stay, such as a new creative team. The other answer DC and marvel often resort to is the notion of trying one-up themselves. Each issue needs to be bigger/better/faster/more than the last one. They'll drop in popular characters or try to tie multiple storylines together.
It can be a horrendously cyclical, and ultimately over-extended, process as they try to top themselves with every issue. At some point, you're beyond the realm of most readers' imaginations. This issue, they save the city. Next issue, the country. Then the planet. The galaxy. The universe. All of time itself. Even though the stakes keep getting higher, the threat to your average bloke-on-the-street is still the same: s/he might die. Whether that's a car running him/her over, or Vogons blowing up the planet, s/he winds up dead. That's where your reader identification comes from, so is there really a difference whether the galaxy blinks out or all of time is erased?
Oni, though, is taking a different tact. While the creators are focusing on just telling a story (and not continually trying to ramp it up to keep readers), the editors have chosen to focus on a lottery/reward system for staying with the book. If you keep reading, you've got a chance of being able to continue doing so for free. Even if the title is one that starts to lose a reader's interest over the long term, the possibility of "free" can be compelling. It might not be their favorite comic, but they're more likely to continue if the only thing they stand to lose is the time they spent reading it.
Granted, you've got to have at least a decent product to do this. Free doesn't mean anything if you're giving away something people actively don't like. (Like I said, I haven't sampled Resurrection so I can't comment on it's quality one way or another.) But that the editors at Oni are willing to make that gamble on this title suggests that they are pretty confident with it, if nothing else.
Now, where I think this idea of Oni's is particularly clever is by tagging the promotion to a dialogue about their book. Not only does this ensure some manner of ongoing feedback, but it also helps to develop a better sense of community. True, Oni has message boards and such available on their web site, but they're not exactly crashing the servers from overuse! Unlike marvel and DC, Oni's titles are generally unrelated to each other so there's less of the inherent sense of all of the publisher's readers seeing the same world through different windows. The Courtney Crumrin crowd doesn't necessarily overlap with Local subscribers in the same way Batman and Superman fans do. So the return of the letters page can help bring together fans that might not even think to visit the Oni forums.
I know I, for one, am curious to see how this plays out. I'll be picking up Resurrection #1 in part to see how good it is, but now in part to see how a promotion like this might keep a book afloat over a longer term. I'll keep you posted on how things go.
* I'm sure Oni will also be sending comp copies out for review to various folks as well, but I'm not even going to attempt to guess what those numbers might be.