Other than emails obvious attributes, it's also a very effective hand raising tool. However, we have a litany of electronic hand raising tools at our disposal. So when we can't reach across the aisle and tap someone on the shoulder, how do we get their attention? If I'm workshifting and I need to reach a co-worker, here are the tools at my disposal:

The first thing I do, in most cases, is check to see if they are "online" using Meebo, or if they have updated their status on Facebook, Twitter, or Foursquare. If I get a sense that they are online I'll send an Instant Message (IM), or Direct Message (DM) via Twitter. In my experience, Facebook is least likely to result in a response because most people are not checking their Facebook in-box very frequently. Foursquare will be able to tell me if they have checked-in, but it's not a good tool for actually locating someone.
The next steps I take depend on how badly I need to reach them. Since it's a coworker I can check their Outlook calendar or shared Google Calendar and see if they have a meeting. If their time is blocked I can wait until their meeting is over or I can send a Text Message. Knowing me, i'll send a text and then wait for a reply. I've found that calling someone typically does not result in a response if they have not responded to the other methods.
If electronic hand-raising is the embodiment of a real person, it would be the obnoxious guy in the back of the room raising his hand, jumping up and down, and screaming "pay attention to me!" This is where the etiquette lesson comes in.
Since these are coworkers that I know personally, I know how to push all the electronic buttons in a way that is least offensive, and culturally appropriate. If I were reaching out the CEO or a Customer, my tactics would be adjusted accordingly. With that said, my coworkers don't want me carpet bombing them with "pay attention to me" messages. All they have to do to avoid the annoyance is go offline, or appear to go offline.
Depending on how urgent the matter is, I think that an IM or Text is the best form of electronic hand-raising. Remember, I'm just trying to get their attention and for whatever reason I need to reach them quickly. In my organization most people have IM and they Text. So if I need to reach them fast, that's the path to getting noticed. The reason texting is effective is because most people don't move five feet from their cell phone. The odds are good that I can get them. Further, it's not good to assume that they are at their office computer. They may be workshifting, in a meeting, traveling, etc. In those cases, texting is the universal shoulder tap.
The key is to not get a reputation as a bell ringer. If you're constantly operating in a state of chaos, you can't expect others to be doing the same. Manage your expectations and set reasonable expectations with your team members.
There are different, unspoken rules about electronic hand raising. What are yours?


