83b election is for the recipient of a stock grant. it won't have any affect on their fundraising prospects whatsoever. it can, however, have significant tax consequences for the recipient of stock (the founders you mention). Also, it really isn't the responsibility of the lawyers to file this. Some will, as a convenience, but actually I prefer to file my own so I know good and well that it has been done. You have 30 days from the date of purchase/excercise to do so. If these guys (the founders you mention) have not purchases or exercised the stock options they were granted, then they are fine. If they did, and more than 30 days have past, then they are not fine, but its not the end of the world.
in a brief, non legal explanation, when you get stock, it typically has a vesting period. And you can't exercise portions before they vest. But, also, the fair market value of the stock increases, so when you /do/ exercise, there is a price difference ('spread'). That spread is considered income by the IRS, and you have a tax burden for that. Wouldn't it be nice to exercise all of it, when there is no spread? Well, that's what 83b is about. You exercise all of it, even before it vests, but also before the prices goes up and thereby creating a spread that is taxable. So there's the benefit. Bear in mind, you still have to wait for it to vest before you actually own it, and if you leave before fulling vesting, then the money you laid out for the exercise of the unvested shares is lost.