Is it really that odd? No. Any company that sells a product will often give some of that products to at least some if not all of their employees. Most of these card companies are really much smaller operations than they appear to be from the outside, so you're only talking about a handful of people. In hard economic times like this, some people will choose to sell items of worth to make the budget closer to balanced, and there's no arguing that the decks in question aren't of worth. It's not the company that's making that sale, it's an individual employee in need of cash. If they choose to sell a gift that was given to them by their employer, they're free to do so. E doesn't make a single buck on any of those eBay sales so you can't lay the blame at their feet.
You're staring at E strictly from a card collector's point of view. That's fine. But their primary mission is to be a magic company first and foremost, and a playing card company second. They make decisions based on the opinions of experienced magicians, not card collectors. Assuming the story about the Infinity being planned first to have black borders on the back is true, it doesn't surprise me that they switched, especially after what happened with the release of Artifice v1. You can complain about it all you want as a collector, but it won't make E become primarily a card company with magic taking the back seat.
As far as the premiums, well - again, magic company first. In fact, company out to make a profit first. It's an old, tried and true tactic for a company to offer premiums for purchases of certain items or certain amounts. Any kid who gets a prize in a cereal box knows this - your parents buy the cereal, you get the prize, period. There's nothing wrong with the integrity of a company based on the fact that they're using prizes to drum up sales. As a collector, this may peeve you, but again - magic (and sales) first.
If you're that dissatisfied with how E does business, there's nothing stopping you from going out there and making a company of your own, producing the decks you like and want to see made. There's no shortage of people chasing that dream and making it a reality. But once you're doing that - running a business, selling products, keeping the accounting books out of the red - I think you'll see E's point of view a lot more readily than you do now in terms of sales tactics.