Email is a wonderful communication medium for technical support. You can take your time to explain the problem in detail and help customer support help you better. Talking to technical support over email is often like interacting with a project's community on an email list with one major difference. Almost all mailing lists encourage you to avoid top posting and most help desk softwares force you to top post. How often have you gotten responses to your tech support questions that go like this:
// Add your reply above here
From: Technical Support
Subject: RE: API not returning the correct response code
Please provide me with the following details
1. Your UserAgent
2. The API User
3. The curl command to reproduce the problem and the output it gives you
You see where this is going. There is no way for me to reply inline and keep the flow of the conversation. To reply inline, I have to copy the original message and then reply. Unfortunately, I have never understood the need for forcing this structure. It does not help in threading (you use message ids and in-reply-to headers for that). If a conversation is getting too long, you can always do gmail style folding for quoted text. In fact, I wrote a small js lib for it.
Atleast for technical support, the reply above this line culture must die. It inhibits me (and I believe everyone) from interacting with support the old fashioned usenet way which just works.