Interesting question but should have included tweeting, perhaps this is covered off by texting, I’m not going to worry over it.
For immediate communication I like text messages but you do have to be very specific about what you write, there is a massive danger of ambiguity when you are restricted to so few words. I also post tweets, often in response to other people’s comments but today I wrote that my SanDisk 8GB card wasn’t talking to Lightroom 3. If you don’t know what this means the brief explanation is that the images recorder on the card are not being recognised by the software on the computer. For any photographer this is bad news but for a pro it could be disastrous. Luckily it was only some interiors, had the worst scenario applied I could have reshot. Embarrassing but possible.
I prefer to talk if it’s anything more than hi how are you. I spent some time this afternoon talking to a guy about an email I had received from one of his colleagues that told me precisely nothing useful and didn’t answer my question. Now that is very annoying. To be fair the chap went out of his way to be helpful, redeeming my opinion of his company. He also acknowledged that they needed a better system to auto respond to emails.
There is no perfect medium for communication, letters, emails and texts can all be misconstrued. Talking to people other than formally can lead to inadvertent slips of the tongue only to be regretted later. Best to keep quiet and don’t write anything down.