Development wonderhouse 37Signals comments about the positive side effect of big text, which is less text.
To be more exact, using a big text size forces you to make sure the text you write is meaningful and free of extra words. This is a great side observation for the trendy Web 2.0 design style of using large text and buttons. In some ways, it’s probably a more important benefit than the actual advantage of larger text being easier to read.
You’ll hear many conversion and sales experts talk about how conversion and persuasion happen with copy. What seems to happen for some sites though, is they take that to the limit and provide too much meaningless copy.
If you have a hard time keeping your copy concise and to the point, try using larger font sizes throughout your site.