I think the most important thing is how the insecure person in question deals with his/hers low self-esteem and insecurities.
The woman mentioned by Learntyoung would be a pain in the ass to be around but I know for a fact that some people can have severe problems in this department without having the need for other people to validate their very being on a continual basis.
I could also use myself as an example as I definately have some problems in this department. It is one of the reasons why I suffer from periodic depression and severe social anxiety but I don't need anyone to validate me all the time. I would take constructive criticism over a complement any day of the week. The former I can actually use to better myself and/or my skills, while a complement would most likely be aimed at something that I already know that I am good at. Don't get me wrong, it's not that I don't want people to acknowledge me for what I am or for whatever skills I might have, it's just not very usefull, it doesn't really yield anything.
I believe that A LOT of people have problems in this department, it's just that most people don't acknowledge this for what it really is. Just take a look around Facebook!
Lots of people, hopelessly fishing for likes or positive comments, often for doing nothing worth any kind of applause.
These people feed on this stuff and through stuff like Facebook, they can get their daily fix instead of having to do it face to face and risking annoing the shit out of their friends.
It's an epidemic, at it's spreading fast, so watch out!