Does your company operate with one CEO or is it lead by two CEO's?

I haven't come across the Co-CEO leadership approach very often but where I have it is within medium sized, usually privately owned organisations. We work with one particular client where the two founders have split the CEO role into Commercial and then Operations / Supply Chain etc... which really seems to work well. The trick they have learned is ensuring they communicate with total clarity beneath them and there is usually one who has a casting vote in any strategic decision making.

I think this works well and considering that most CEO's have an experience bias towards a specific function it can provide an unbalanced view to the business?