Long-tail searches? Are they effective?

I came across on the Digitalpoint forums section on Search Engine Optimization (SEO), and I've found this latest SEO topic on long-tail searches? What are long-tails anyway? These are names of websites or keywords/keyphrases with long letters and words. But are they gonna take effect on our Google rank? One who commented says that long-tail searches are not new, because they are so-called multi-word phrases such as "how to apply for a credit card online", which we count as 8 words actually. So it's considered long tail. For short tail searches, at least 2-4 words will be good enough, and may help you generate traffic as well. They are not a new set of scheme, and it may truly not going to improve or reduce your Google PR.

Just stick to short tail searches!