What is the purpose of a beer foam scraper?

Foam has always been perceived as a "bad pour" in most taverns, however, it is good for beer to foam. The foam allows some of the carbon dioxide to escape before you drink the beer.

Nevertheless, this condition created the need for foam scrapers. This unique device looks like a tongue depressor. After the bartender poured the beer, he would use the scraper to swipe the foam level with the rim of the glass.

http://home.earthlink.net/~mrsfanatic/id16.html

I don't know where the above comes from, but in the UK a head on the pint was always regarded as essential. Getting a top-up if it was too large (in the days before oversize marked glasses) was also necessary. This is still the case with those of us that drink proper ale. Just looked - yes, they're talking about American beer. I'd refuse a pint if anyone had wiped a stick across the top of it. (Then again, I probably wouldn't be drinking a pint of American fizz...)