I'm referring to the trend to fit dark coloured carpets, (chocolates, dark greys etc). The issue is to do with risks of chemical damage to these carpets. It has been common for a long time, but moreso that these dark colours are so popular.
Recently I cleaned chocolate carpets in 5 rooms of an 18 month old well kept home. They had two teenage daughters. Both of their bedrooms were in good condition, except they had 'bleach marks' on them, where colour had been damaged by contact with certain substances.
But that's just an example of the problems I see frequently. Here are some others;
Teenage boy applies his Clearasil and then does his push-ups on the carpet.
Cleaning lady cleans up that spot on the carpet with the spray & wipe.
Mum cleans the windows, dripping Windex from the leaky bottle onto the carpet.
Teenage daughter takes off her wet bathers

Carpets need cleaning, and the cheap '5 room special' seems like a good thing.
Accident happens, and Shannon Lush's book 'Spotless' is followed.
You walk through the carpeted room with the wet cloth, hoping the bleach doesn't drip.
In all of these cases, inappropriate chemicals or substances may be contacting the carpets. At first, nothing happens. But then, gradually after a few days or weeks, strange spots or patches appear, where the products oxidize and the colour is fading or changing.
Here's the deal. Carpets are supposed to conform to standards for colour fastness, and most do. However, strong alkaline chemicals and those with oxidising agents (peroxides in acne creams, tinea creams etc) will destabilize the dyes, and sooner or later, the colour will be affected.
So, you had better be careful. Don't use any chemicals on your carpet unless you KNOW it is safe. Don't follow wives tales. Don't use products around the carpets that are alkaline (window cleaners, spray & wipe etc) or bleaches. A common cause is spray bottles that leak and dribble.
And only use professional technicians that clean to Australian Standards when cleaning is required.
Ash.