Humble Bundle Thoughts

I first don't think that the revenue through customers with prepaid cards in relation to regular CC's or PayPal is that big (though the only one with a safe answer might be HB themselves) and second prepaid cards are easy to abuse and commit fraud with - especially in this regard and with a recurring subscription like the HB monthly they're bound to create a lot of problems sooner or later.

And I don't think that the weeklies are on a decline (Saints Row, Telltale, Capcom - okay, besides that Gamemaker thing and the current one, although it might be as simple as the games offered in the latter just not being my taste ;>) and from a value standpoint the amount of stuff you get for the price you have to pay has never been unfair, on the contrary.

I know the United States are very credit-card centric but unless it works differently there you can use PayPal linked to your bank account (not completely sure if you have to set up direct debit for that or if linking them suffices).
As an added bonus contrary to credit cards (AFAIK) there are absolutely no fees.

And on topic: I'm pretty sure for their normal bundles they take whatever semi-decent games they can get. At least that would explain why they keep repeating the same ~ 12 developer bundles. Pretty sure it's easier to convince a publisher to sell one of their games in a 12$ blind Bundle than in a 1$ / 5$ one where you know what you get in advance.

Summer is usually a down period for bundles. If you look at Humble's bundle history, they've regularly been very light around August. Your concerns may or may not be valid, but as bundles sometimes haven't picked back up until November, it may be a while until we can get an accurate read on that part of the matter.