IMO, the industry as a whole has not educated the consumers very well.
here are a few things everyone looking to buy carpet should know.
there are 3 synthetic fibers used to make carpet. Nylon, Olefin(polyporylene), and Polyester.
Nylon- Extremely durable, nearly impossible to abrasively wear the fiber, extremely resilient, technological advances in stain treatments have greatly improved nylon's stain resistance.
Olefin- Most commonly used in berbers and inexpensive commercial loops. Also used in high end woven patterned pieces from europe under the name of Eurolon. Good resistance to abrasive wear, weak in the resiliency category- it will matt and crush down, extremely naturally stain resistent, virtually impossible to stain the fiber or bleach the color out(it can be done but is difficult to do), low melting point, has an affinity for oil. This fiber is good in loop construction(berbers) for light to medium traffic areas and for areas such as basements where spills are going to hapen from the kids or partygoers.
Polyester- this is the green fiber. a good amount of this fiber is recycled plastics mainly from plastic beverage containers. very naturally stain resistant. resiliency is in between nylon and olefin, good maintenace will dramatically slow the matting and crushing however it is going to happen. the majority of products made from this fiber are of staple yarn construction. it will shed alot for the first 6-12 months and all staple products will shed lightly for the life of the product. The benefit from this fiber is it's natural stain resistance and it costs a lot less than nylon so you can get that thick soft plush on a much smaller budget.
If i had my way the only synthetic fiber that would be used to make carpet would be nylon. olefin and polyester are going to matt, crush and ugly out. if you have a family of 3, you can expect to see this within months and by the time you see it, it's too late to reverse.
The tighter the twist, the denser the pile, the better the carpet. the taller the pile the more it can move.
warranties-
wear warranty- the fiber will not abrasively wear out more than 10 % for the period of the warranty. i have never seena carpet made from a synthetic fiber abrasively wear unless it was severly abused. I have also never had a claim approved for true abrasive wear.
texture/appearance retention warranty- this warranty states the fiber will not lose it's texture as a result of the tufts losing their twist under normal foot traffic. This does not cover matting and crushing. matting and crushing is considered normal appearance change from use and is not caused by the tufts untwisting. The main cause for matting and crushing is soil in the pile. proper maintenance and the right fiber allow this condition to be prevented or corrected. The fibers are heat set to hold their shape and it is a rare circumstance that the process at the mill failed. one of the main reasons the mills recommend or require hot water extraction is the heat helps the pile bloom back up to it's original shape, especially nylons.
stain warranties-surprisingly, these are the best warranties on carpet. they do honor them. you have to jump through some hoops but if you have a legitimate claim, it will be taken care of.
for any performance claim, you have to provide your maintenance receipts. Depending on the fiber/carpet manufacturer, you have to have proof of maintenance at a MINIMUM of every 18-24 months and the last service has to be within 30 days of filing the claim. the consumer is the one using the product and is responsible for maintaining it.
lastly, remember that some of the warranties are prorated and some of them,not all, but some do not cover the replacement labor, they only cover the material.