Tabs can become a nightmare if you happen to be forced to use a tool (e.g. a debugger) that uses a different tab width than you editor/IDE. For example, many tools use a tab width of 8 (which is the default tab width for HTML) which is far too wide for indentation.
This is not an issue as long as you stay within you IDE, but then you can configure you IDE to convert tabs into spaces automatically. "Tabs are configurable for personal preference" \- Some people seriously seem to suggest that within the same team different people use different identation widths by configuring different tab widths. To me this is just a crazy idea.
