I don't think it's quite the same as italics--there's overlap, but lots of differences, too.

I use italics for emphasis in a polite or serious way, or to identify foreign words. All Caps is for emphasis in an often cynical or sarcastic way, though it can be simple emphasis depending on the context.

Ex.

Valentine's Day in Japan is very different: women give men chocolates.

-but-

I went out with my co-workers last night and I am STILL DRUNK.

-note the overlap-

In Japan, people are very generous and kind.

=

In Japan, people are VERY generous and kind.

However the Vday example would sound different if the italics were changed to all caps, and the drunk example would just sound stupid.

I suppose the thing I've seen people use that is similar to all caps is the pseudo underline using the _, as in People are _crazy_ here. But it really only works for one or two words.