Paypal cannot be used for pre-orders. Paypal's policy, not Stardock's. Paypal will be allowed after the game (or maybe the Beta) is released.

Yell at Paypal not Stardock.

Are you sure about this? I've used Paypal to pre-order things, admittedly music CDs and not games, so I wonder if that policy only applies to digital DLs or such? As if so, wouldn't it be possible to set up a pre-order for a physical copy, plus shipping?

Paypal is used for direct transactions. So when you pre-ordered your music CD you probably had to pay for it directly, even though you were going to get it at a later time. Stardock does not charge you immediately after you pre-ordered Rebellion, that's why they cannot use Paypal right now.

Yes, it is because Stardock is to much honest... they don't receive a cent before they deliver really something... not like some other who use money from pre-order to finance their game development...