...At least not in my world.

After years of doing it correctly, I have gone and purposely done it wrong over and over again.  I know what is considered right (no double space) and what is considered wrong (double space), but after years of doing graphic design, I no longer follow that rule so closely.  I have two exceptions I personally follow, and nobody has ever noticed until I point it out to them (and then they chastise me for not knowing the 'correct way').   I know that professional typesetters use 1 space, and I know that typing teachers taught 2 spaces, and I know why.  In professional printing, you have what are generally well-designed typefaces with professionally tweaked kerning that shouldn't need the extra space.  For the old-fashioned typewriter, however, the text was in a fixed-width typeface (kinda like Courier) that did not aid the user in his or her reading of the text.  This drove the need to insert that extra space as a clue that the end of a sentence was coming (since people often see ahead of where they are reading, such cues are important).

For instance, in multimedia (which includes web design), your screen fonts are often not well represented in pixels and many characters butt up against one another while others space out further.  Kerning just doesn't seem to take care of that very well, as you can see in Word documents (or the occasional web site) that have been justified.  Since here we tend to lose the advantages afforded good typefaces in print, namely proper kerning and clean representation of the fonts within the small amount of pixels allowed, we lose our reasons for abandoning the double space.  In these cases, I add an extra space after a period to improve readability.

When using free fonts (from great sites like Chank), often the characters aren't properly spaced, and they need some help from the designer.  Again, sometimes you don't want to kern the entire document; you just want more space because the font designer made his period have no space on the right.  In this case, I will use a double space.  I have found that in print, most designers tend to not notice this until I point it out.

I used to follow the rule precisely, but after years of looking at my stuff and being disappointed at legibility, I made the conscious decision to abandon or modify that rule in certain cases.  Rules are made to be broken, aren't they?

I was reading an article from Scientific American while riding on the tube the other day, and I ran across the following block of text:

"...to determine whether they were commercially viable in the U.S. Ware and his colleagues concluded that the green and the brown cotton yielded too little..."

When I first read it, it took me a few times of re-reading to recognize that Ware is a person's name (as explained earlier in the article, I just forgot since I am bad with names), and not some government agency (US Ware?).  The single space in this case, coupled with the justification of the article (removing the consistency of spaces between words from line to line) confused the heck out of me.

I found myself wishing they had an intern who incorrectly added another space after years of being traumatized by an unruly typing teacher in high school, because then I wouldn't have been so confused.