[cowiki-dev] Tabs vs spaces -- what's the downside?

I have heard some strong opinions on using spaces instead of tabs. 
I've never understood this, because I've always assumed that everyone
can use tabs and configure them neatly.

What are the disadvantages of using tabs?

Are there common applications which cannot display tabs properly?

Are there cases where one cannot type the tab character?

Are there common tools which cannot be customized to make a tab
display as 'x' characters of whitespace?


I honestly don't understand using spaces, because .. it's extra typing.  =)


I ask this because I'm just starting to learn a little bit of
programming, and I'd like to learn more about common practices like
tabs vs spaces.