Typing two spaces after a period is wrong

We cannot help but agree with Farhad Manjoo, a technology columnist for the New York Times, typing two spaces after a period is totally, completely, utterly, and inarguably wrong. 

Until the 20th century, publishing houses and printers in many countries used additional space between sentences. There were exceptions to this traditional spacing method—some printers used spacing between sentences that was no wider than word spacing. Termed French spacing and synonymous with single-space sentence spacing until the late 20th century. With the introduction of the typewriter typists used two spaces between sentences to mimic the style used by traditional typesetters. Although the wider sentence spacing was phased out in the printing industry in the mid-twentieth century, the practice continued on typewriters and later on computers. Perhaps because of this, many modern sources claim that wide spacing was created for the typewriter.

The desired or correct sentence spacing is often debated but many sources now agree that the additional space is not necessary or desirable.