Assets held by Scotland's banks, including bailed-out Royal Bank of Scotland, are worth more than twelve times its gross domestic product (GDP). This is a much larger multiple than that of Iceland's in 2007, for example, just before its 2008 banking collapse.
Scotland's departure from the U.K. could also threaten the country's international standing, shrink its army and even have consequences for its nuclear deterrent – many of the U.K.'s Trident nuclear missiles are currently located in Scotland.
And there are concerns that, if Scotland becomes independent, the question of Northern Ireland's independence could rear its head.
(Read more: Ukraine for Russia, just like Scotland for UK: VTB Bank CEO)
The "Yes" campaign, however, say that an independent Scotland could control the North Sea oil revenues. It also argues that left-leaning Scotland fares less well when a right-wing party like Cameron's Conservatives, which has embarked on cost-cutting reforms to the benefits, legal and healthcare system, holds power in London.
Rupert Murdoch, the News Corp media tycoon who has Scottish ancestry, has backed the "Yes" campaign in the past on Twitter, but the Scottish Sun, his main newspaper interest in the country, has not sided with either the "ayes" or "naws" so far. Other businessmen closer to home back the campaign under the umbrella of the Business for Scotland group, which says it has over 1,300 members.
"While David Cameron is focused on narrow arguments of national identity, substantial economic evidence has confirmed that Scotland will be a wealthy independent nation," Gordon MacIntyre-Kemp, chief executive of Business for Scotland, said.
"With such a strong fiscal position, combined with our natural resources and the resurgence of Scotland's entrepreneurial spirit, independence is the business opportunity of a lifetime."
- By CNBC's Catherine Boyle. Twitter: @cboylecnbc.