As someone who, despite being 24 years old, learned to type on a (mechanical!) typewriter, I don't like tab for indentation on the basis that, for me, tabs have a very specific meaning:

Carriage (or cursor, if you prefer), go to the next tab stop. [2]

For typewriters it means to go "literally" to where the next stop is. For text editors (at least for emacs)[1], it means to insert as many spaces as needed so the next column on the current line matches with the last non-space column on the previous line.

So, in the same way I use the table tag for tabular data in markup, I use the tab key for tabular text.

[1] http://www.jwz.org/doc/tabs-vs-spaces.html [2] http://en.wikipedia.org/wiki/Tab_key#Origin