Here's an interesting comment by Alex Novarese in Legal Business. He distinguishes between criticism of partnership as a business model and the actual behaviour and expectations of law firm partners in relation to capital investment and innovation.
Here is a personal view: the model is often confused with what it means to be a lawyer. Partnership has been successfully deployed in creative industries like advertising and architecture – it's an effective structure for engaging strong-willed, high-achieving individuals. Much of the criticism laid at partnership's door is to do with the psychology of lawyers – both the kind of people attracted to it and inherent professional obligations – which promotes conservatism and risk aversion. But some of that scepticism is what we need lawyers for. Partnership in itself is not a bar to innovation. The biggest structural issue with partnership is full distribution of profits, but that can be resolved. This is a major point: you often hear talk that law firms need outside investment. In reality most large law firms generate huge amounts of capital, easily enough to fund their activities and investments over the medium term – they just choose to keep giving it away and thinly capitalise their businesses.