Choosing the right keywords is crucial to search engine success. If you choose keywords that are too broad, you will have difficulty converting visitors into buyers. If the chosen keywords are too competitive, you may become "lost in cyberspace".
It is best to choose keywords that are highly relevant to your products and services. For a customer wishing to sell Plasma Televisions it is better to target the keywords "plasma televisions" compared to "electronics" or "TVs". Aside from individual keywords being to broad, they are also very competitive.
The best-case scenario is choosing keywords that are both targeted and popular. Optimizing your website for keywords that no one is searching for is a waste of time and money.