I understand the thinking, it is assumed that if they only get a tricke of traffic and if they are "low competition you will be able to find loads of these words and easily dominate. But sometimes if not alot of times it does not work this way. Chances are if the search term does not get that many searches in Google, it probably does not get that many on article directories.
Where am I going with this you might ask? I am saying you should not be afraid to go for terms that have a little competition. If you want to get loads of traffic when doing things such as article marketing you need terms that get searched.
Now I am sure some people have tremendous success with long tails, but most get sub par results. If you are able to rank for one of those low competition low traffic long tails then great. But most of the real value these days is to be found in words that others are too afraid to go after.
So tell me what would you guys prefer, a bunch of long tails that are still hard to rank for or a few keyphrases that offer less competition and have more taffic? These key terms give the illusion of being hard to rank for, but when looking closer you see the sites at the top can easily be beat out.