In telecommunications, net gain is the overall gain of a transmission circuit. 

Net gain is measured by applying a test signal at an appropriate power level at the input port of a circuit and measuring the power delivered at the output port. The net gain in dB is calculated by taking 10 times the common logarithm of the ratio of the output power to the input power. The net gain expressed in dB may be positive or negative. If the net gain expressed in dB is negative, it is also called the "net loss". If the net gain is expressed as a ratio, and the ratio is less than unity, a net loss is indicated. The test signal must be chosen so that its power level is within the usual operating range of the circuit being tested.

From Wikipedia

"COMMERCIAL ENTERPRISES ARE RELATIVE newcomers to the on-line world, and so far few of them have made money there. Most businesses on the Internet and other networks today do little more than advertise their wares on "billboards" on the World Wide Web in the hope that a passing surfer will stop long enough to buy something. These old-media advertisements, dressed in their new-media clothes, are only one indication that marketers have yet to discover the secret to unlocking the revolutionary potential of the Internet and other networks".

John Hagel III and Arthur G. Armstrong, NET GAIN, Expanding markets through virtual communities