I’m not sure what the social etiquette is however search.twitter.com is such a ridiculously useful tool.
You can search for “moving to Melbourne” and find everyone who is moving to Melbourne. Great marketing tool for a removalist business don’t you think?
If you are working with teen depression why not search for “I am depressed” and set the location to “near:Melbourne” and you will find people who are depressed at that moment.
Facebook also allows you to search friends and EVERYONE’s posts real time.
This is awesome!