Personally, I generally avoid pre-ordering from places that require a deposit on their pre-orders. I understand why they do it, but from the customer point of view, it's too constricting when you've got 8-10 months of wait time to contend with.
I would think Sideshow would welcome some of their exclusives being on second chance or coming back into stock. Why do you want all of your exclusive items sold out during the pre-order process? Doesn't look good for new collectors who discover the site for the first time, yet are discouraged to order because nothing is in stock. Also, not everyone rushes to pre-order items. There have been many occasions where I've eyed pieces I was interested in, but waited until shipping. And to my pleasure found that the exclusives came back in stock and I ended up buying them: Evil Queen PF and Vlad being two recent purchases that come to mind.
Seems to me Sideshow is implementing this policy on lines they deem to be popular, like Marvel. I'm guessing SW and TMNT would fall under this category as well, while other lines would remain untouched. Doesn't seem fair to me to do that. Either implement the policy site-wide or not at all.
And I find the whole business of focusing on the "serious collector" ridiculous. Yes you have the flipper and the chronic canceller, but what do you define as a "serious collector?" Someone who pre-orders everything? Someone who spends X amount a year? Someone who values the piece for itself and not it's increased value? Someone who orders from Sideshow and no where else? I just feel it's a poor reason. They want to cut down on the volume of cancellations, plain and simple.