There has been plenty of publicly listed fruad, it's just harder to do....
While there has been no actual public evidence of fraud, the issue is that making the company's financials available to private investors isn't the norm. Those disclosures are mandatory when dealing with financial institutions, and in most cases, accredited investors. So it's easy for them to issue shares without having to disclose any actual detailed financial statements to an investor. All they can do is present "top level" numbers which, if fraudulent, is what tends to land people in jail. e.g. all the people who invested with Madoff, didn't get to see the company financials, or they wouldn't have invested. It's also why Bootcha, one of the early stage investors in the project, got his money back when he asked for the financials.
It's also why the SEC came up with new guidelines and support for unaccredited investors via the JOBS Act; and under which companies like FIG, StartEngine etc operate in some cases. Those guidelines protect smaller investors and give them rights they otherwise wouldn't have if, like the Star Citizen backers, they were just throwing money into a fire pit.
In most cases, the paperwork explicitly prevents access to financials like that. Even a public company, which has to make its financials available, doesn't have to disclose every little detail. e.g. we won't know what the CIG-LA space door cost, because that item can be buried in other expenses. You can take a look at the public (it's the law in the UK) filing for Frontier (devs of Elite Dangerous) and have an idea.
However, when companies get sued, and it's related to financials, then all that paperwork gets compelled into discovery. It's why Crytek was able to make those demands for the financials because monetary gain is material to their claims. And it's why CIG freaked out and filed a protective order to delay it.
It's also why State and Fed govt agencies (IRS, FINCEN, FTC, State and Attorney Generals etc) who then dive into details can uncover fraud when they start following the money. They get to inspect every little detail, who got what, when, how etc. It's also why in ALL cases of financial fraud, there is ALWAYS a charge of "wire fraud" and "bank fraud" because as long as funds went through a bank, and was moved from A to B, it will fall under those guidelines.
In the case of CIG, unless they were stupid enough to actually flat-out engage in that, it's going to be very difficult to prove fraud - of any kind. Things like malfeasance, unjust enrichment etc, are easier to allege and prove - due to their nature. If they however presented bogus paperwork and numbers to either an investor (of any kind), a bank, a tax authority etc - and the intent was to commit fraud, that's when people go to jail.
If you go back and read the crowd-funding cases which have been brought by States or the FTC, you can see that there are no allegations of fraud because it's a very huge bar to cross and get to.
