[DuoSRX]

$AAPL is used on twitter to talk about stocks, just like # is used for hashtags. Like $AAPL, $GOOG, $MSFT ... etc

[astrodust]

Ah, Twitter. What symbol will you appropriate next?

[maukdaddy]

Probably %

[kanamekun]

@astrodust - Perhaps the @ sign? :-)

I actually just looked up hash tags on Wikipedia, and was surprised to see that the asterisk is starting to be used to give out "stars" and ratings to items: http://en.wikipedia.org/wiki/Tag_(metadata)#Star_tags

So I guess so far, microblogging has appropriated at least four symbols: @, #, $ and *. That leaves: !, %, ^, &, and ().

[syncsynchalt]

Could it be... interrobang‽

[cookiecaper]

Why is that necessary? Why not just use the symbol? I'd think that $ appears in too many non-stock contexts to really be a useful filtering mechanism.

[rkudeshi]

IIRC, it's because of StockTwits. http://stocktwits.com/