Why would 340 points/few weeks membership be considered a "Top Contributor?"?

Anyone at any level can become a Top Contributor, number of points and level gained have no bearing on gaining the TC badge.

"A "Top Contributor" is a member of the Yahoo! Answers community who has shown that they are knowledgeable in a certain category. Each user can be a top contributor in a maximum three categories."

The TC badge is awarded on the number of questions answered and best answers received by the user in a particular week, in a particular category.

It is rumoured that you need at least a 10 percent best answers in your chosen category to get a TC badge although the actual percentage and the number of answers is Yahoo's secret.

All you see and read on the subject is unsubstantiated speculation, rumour, assumption, imagination, and guesswork.

A user who is on the leader board may or may not have a TC badge, the criteria is measured on weekly participation in a particular category (number of answers and % of best answers in the category).

The easiest way to get a TC badge is to concentrate on one category where many questions are asked and hope to get some best answers.

The Polls and Surveys and Jokes and Riddles categories do not have Top Contributors.

If you have contributed enough to meet Yahoo's criteria, the orange badge will appear below your avatar on Monday morning.

It can disappear just as easily on Monday morning, if you don't keep answering questions in your chosen category.

It has nothing to do with the number of points or time of membership. It has only to do with the percentage of Best Answers -- in a focused arena. If a person only answers in one category and manages to get about 10% - 15% BAs in that category, they get the label. I managed it in one category with 12 answers and 3 Best Answers, which took all of 20 minutes to do.

It is rumoured for you to get a top contributor badge you need to get and keep a 10% best answer percentage in one particular category. You are able to have as many as three badges at one time, but you do not get one for the Entertainment category. They are given out every Monday morning when the points are updated. They are just as easy to lose as they are to get. Also you have to be really careful when you get one because once you get one trolls will attack you and try to get you suspended.

they need a loser badge.