I woudn't use it. I'm not going into detail but two areas are obvious:
The monetary issue: The current currency model evolved as a dominant means to exchange goods and service for a reason. It's flexible. You can exchange your money to almost everything. It's also transparent, because prices signal scarcity and you have some sort of feeling for 'fair' prices. I also serves as a store of value.
The legal issue: A similar argument applies to our legal system. It may be complicated but this is because the issues it tries to control are complicated as well. There's so much that can go wrong in an agreement. Legal rules are tested and formulated to cover many common problems.
With this in mind, let's look at some specific problems:
What's the fair price in virtual stocks for some work, say designing a web page for a start up? Any contributor would need to consider the chances of the startup to make money, otherwise he may just waste his time designing web pages for 'bad' companies. The same holds true for the founder: How many shares should he spend for design work?
While everyone gets a share of the revenue (so it seems, at least), what about sharing the costs? Nearly all companies have (additional) costs but these don't seem to be shared. To do this, you'd need to track all your costs in a virtual accounting software on the platform.
What about sharing other means to make incomes? Let's say a designer makes a web page for someone and then, the startup builds a second income stream somewhere else, using the web design. Theoretically, the designer should get a share of the income, too, but unless this is tracked by the platform, how will he know it exists?
What happens when your start up makes income? You get the money based on your shares but selling your start-up will be hard. For you'd need the agreement of all the share-holders. On the other hand, what if the startup you have shares with, sold some additional shares elsewhere? Or raised additional money from friends and family?
In all these cases, there're additional transaction costs for founder, co-founders and contributors. They basically need to act as VC investors, trying to estimate the chances of success for each company. At the same time, they need to rely on the platform's legal rules and accounting to make sure it works. But who's going to be the judge when conflicts arise?
At the same time, it doesn't provide any real benefit, does it?
The majority of potential contributors is outside the platform -- you can get freelancers for nearly everything you'd need as a software startup. The majority of potential co-founders is also outside of the platform.
Finally, there's the problem of adverse selection: Startups, co-founders, and contributors who do have a good product or make exceptional work, don't need such a platform, I'd guess. This means, those who do use it, are (to some degree) those who have more risky or less convincing products or provide work that's not that exceptional.
I'm sorry if that sounds negative, but you did ask about potential problems. Yet, maybe it helps.