Turn the question around: what shouldn't be revealed? And why?
Salaries are one area where most say it shouldn't be shared. Why not? Many governmental organizations have all their salary and benefit information available to anybody. You can know exactly how much the local sheriff makes per hour then estimate yearly based on overtime, etc. Is there some problem knowing that you are getting paid more or less than subordinates? Aren't salary surveys fairly common and many HR departments subscribe to such things?
Sharing the financials is interesting, but could share the entire balance sheet. What if you crowdsourced (via your trusted employees) cost saving measures? I know local PTAs know are trying to come up with solutions to budget shortfalls for local schools and I've seen some rather innovative ways they handle things -- tough decisions, everything on the table, those who want to contribute can do so.
I think the main reason things like financials are kept relatively secret is because of stock market speculation -- if you could view the entire balance sheet plus projections for every company you are considering, would market speculation disappear? Does it then become a matter of modeling roughly as complex as hurricane predictions or it is easier than that?
Developing new lines of product, anything still pre-patent, contract negotiations with suppliers, renters, etc., are all things that contribute up and down the line with the overall balance sheet. These are things where the details maybe shouldn't be shared publicly, but maybe within the company or division?
Who your biggest customers are and what their pet peeves and pleases are, these are things that maybe should be shared widely (CRM does a lot of that).
Re: Tesla -- it would be nice to know what they are working on for the Model S. Full stop. We might not be able to change it, but we'd be able to make better decisions regarding our own purchases and plans. Ask your customers and prospects for a priority list. I'm not asking for info re: future designs, because one reason to withhold information is prospects holding off on a current purchase to buy future version with feature X instead.
Here's a sample off the top of my head of items that I think need to be better communicated, limited to items that make a difference of a sale or not to some folks (these mostly don't matter to me frankly):
Center console -- we've seen Alpha, Beta, and variations in between. Brief reviews have mentioned the delivered design being unusually sparse.
What are the design constraints? What are the current solutions? (Design drawings are ok) How are those solutions expected to be delivered to already shipped vehicles?
Charging Adapters -- UMC comes with what? What are the plans for adapters already deployed and ones still in standards committees? A subsection of this would be the technical challenges relating to supercharger access for 40 and 60 Kwh packs.
Right now I can't think of any other big items. There are a bunch of little things, but I doubt somebody is going to purchase or not purchase based on a little item and I'm limiting myself to just items in the current cars.