Explain why you will or will not be making alts. I don't think there is a lot of info released about creating and using alts. We know we can make several with one account (4?).
People usually create alts so that they can specialize that character in manufacturing and/or market trade. ESO will allow for a lot of skill points but with so many skill lines potentially available, I'd imagine that a lot will be making alts to free up those lines for more notable skills.
People create alts on a completely separate account. This allows for users with multiple systems to have two or more characters, not only active at the same time but grants the ability to interact between them directly. Not sure about the limitations there. I mean as far as the character having to be in the same alliance for that to be possible.
While some will create alts from the stat, others may make them after 50+ and 50++, as... just another character with no intent of contact or acknowledgement the other character even exists.
A question that sparked my initial concern was... How will we trade with our alts in ESO?