Question: I noticed that "dame", which means "not good" or "don't do that", is sometimes written in manga as katakana. I was wondering, is it because katakana is used to express a strong feeling?

Sometimes, there are also other words written in katakana. In general, what are possible reasons why people would choose *katakana* for a word instead of *hiragana* or *kanji*, especially when that word is not usually spelled with *katakana*?

Answer: 
* Style - Simply as personal style
There are various reason depending on situation. Yesterday i saw a frog shaped earpick on which it was written カエル instead of かえる. I asked about it and i was told that these things are done so as to avoid any confusion about the product or the instruction given for the user or consumer. かえる can also mean to return , or to change. Also some people can't read Kanji. These are the reason that leads to writing some catchy phrases or words so that there is no ambiguity between both parties. These are informal...

edit: to grab eyes as well...