How do all those upset people complaining about offering incentives deal with something like Kickstarter? That's all about speculating on an unproven product, and buying into rewards for doing so, rewards that can't be had unless you invest in the product early.
Seems to me the problem with D&DBeyond is that they appear to be very very close to WotC regarding the nature of their partnership. The boundaries seem to get fuzzy--exclusive videos, etc--that seem to carry implications that D&DB's content is going to somehow be more "officially legitimate" than another 3rd Party Licensee's. The nature of their relationship seems to imply that potential exclusivity could be possible in the future, and as is typical we RPG gamers ramp up the speculation and draw conclusions because we've learned that sometimes those conclusions are accurate as much as they pan out to be false. There's a history of that in this industry, I think, and people are wary of getting promised something and then getting burned. Ultimately, what's offensive is the potential for official content behind a paywall.
On the other hand you have people saying this is a regular marketing tactic that isn't unusual. It's common to do this. And it works. And because they themselves say they're writing the content (whatever it is or might be in the future) it can't truly be "official", so there shouldn't be any worries. Our "completionist" genes, or our "responsible access" instincts don't need to take umbrage.
I think it all depends on how you view WotC's relationship with D&DBeyond. It's clear it's not like their relationships with Roll20 or Fantasy Grounds, but frankly we don't know that much about what it is nor what it might be used for in the future. And that makes us regret investing in one platform or another. And the lines between what is offered by any of them become more evident, and the distinctions become more important.
But underneath all of that is the unsettling potential that we cannot have it all. The idea that "official" content might only be accessed through specific platforms is unsettling. Mind you that exclusivity has been around for years--ENWorld's has pay-for-content offerings, for example. But what makes something "official"? What is the advantage of "official"? Is it edited better? Is it playtested better? Is it somehow imbued with proper vetting that makes its quality during play better? Does it really reduce the amount of time DMs need to examine content when it has already been "carefully examined" somehow? By whom?
Does the stamp of the rules-gurus legitimize the content of the game when it's obvious they can make mistakes themselves, that the web of rules and balance they've created is not foolproof? Or even when they say, ultimately, rules are up to each individual group playing experience? Does playing with official content only automatically improve one's game?
Why do we invest more in supplements/material that look and feel more similar to the original gaming materials, imbuing them with legitimacy? (Seriously, going through the Homebrewery and looking more legit doesn't make it higher quality...)
And, thus, does material coming from a company with an obviously unique relationship with WotC herald exclusive official paywall material?
Personally, I'm not sure I care that much... I can't consume it all anyway. Let it flow.