If it uses two-space indents, it's corporate code; if it uses four-space indents, it's open source. (If it uses tabs, I didn't write it! :-)
I hate spaces (within source code) for some reason. Fortunately TextMate makes working with tabs and spaces trivial. I can easily convert spaces to tabs and vice versa so this really isn't a problem with any sane file that uses either consistently.
But what I'd really like to see, is a control character for indenting source code. It shouldn't be too hard to implement it to any modern editor and it would eliminate all (or at least most of) the whitespace-hassle if it would be mandatory. And for an added bonus, it would force using of unicode.