Common sense would dictate that for the purchases to function as a revenue source they must interrupt the flow enough for users to be prompted to pay.

FORBES: Windows 8 Killed The Start Menu, But A Startup Named Pokki Brought It Back

This unchecked flow of data is a new source of sensitive information and creates security loopholes for serious cyber attacks.

FORBES: Social Media: A Nightmare For Enterprise IT Security?

At present, 80% of Russian gas exports to the EU flow through pipelines across Ukrainian soil, a source of ongoing tension.

BBC: Nord Stream gas pipeline opened by Merkel and Medvedev

Water for People recently teamed up with Akvo, a Dutch open source software company, to help develop the FLOW's (now officially called Akvo FLOW) features and international reach.

CNN: Going with the 'FLOW' towards better sanitation

Its housing guide is a good source of advertising revenue since housing management companies generally have regular cash flow.

FORBES: Wharton Start-Up, Chattersource, Helps Students Find Housing, Haircuts

The flow of cash from Filipinos working in the Middle East is also a source of concern, given the discord in the region.

BBC: A rickshaw pedals through flooded streets

Security Council resolution also authorizes actions to try to prevent -- try to work with the neighboring governments to try to prevent the flow of mercenaries into Libya so that he cannot draw upon that as a source going forward.

WHITEHOUSE: Press Briefing

Using business aircraft to provide a dimension of air transportation that the airlines do not, entrepreneurs and companies are enhancing the ebb and flow of international commerce throughout Africa, a continent with vast potential as a source of natural resources and opportunity.

FORBES: African Business Takes to the Skies

But at least one source who has seen the building's books says the buyers will be buying a small amount of negative cash flow while making a long-term bet on the building's eventual profitability as the most prominent and expensive asset in midtown Manhattan.

FORBES: GM Building Sale Shows REIT Resurgence