I modified according to Justin and Jan's suggestions. And also added support for row vector. It is much faster now. See the updated file at http://www.mathworks.com/matlabcentral/fileexchange/47055-cell2csv-m
credits go to Sylvain.
A very convenient code. However, it is a little bit slow for saving large tables.
Jan Simon's suggestion is very helpful. Another way to further improve its speed is to bundle the output to fprintf() as much as possible. For example, write a whole line at one call rather than call fprintf() for each cell.
These two tweaks can reduce the excution time by >60%.