I think most agents call when they offer representation (that's why it's called "The Call" LOL). As do most major houses (although if you have an agent, your agent will give you "The Call" that you've sold, too).
Would I automatically assume an agent was wonky if they did 'the email' instead of the 'the call'? No. Especially if there were good reasons. But I'd DEFINITELY make sure I asked all my very important questions via email and pay very close attention to the answers. It would probably be a mark in the 'weird' category, but not a deal breaker.
Well, that's why I mention having so many personality questions in the Very Important Question list at Passionate Pen. Personality and how an agent works is going to be VERY important in the interpersonal relationship.Also, a writing friend of mine had a very good agent, but after her book was accepted by an editor, the relationship between writer and agent began to fall apart. It turns out that they had very different personality styles and this seemed to be something they could not overcome. How important do you think this is and is this one of those things that we have to figure out by listening to our gut?
One way to avoid this happening is to really think about what you need/want from an agent. Talk to other authors, read agent blogs, these things will help you determine if you're being reasonable in those expectations. Then, when you get "The Call", you can ask specific questions about what YOU want. Before you sell and after.
The problem is that sometimes authors get so wrapped up in the "Yes" that they don't realize it might not be the best thing for them. It's a hard business and there are so few yeses that it's an easy mistake to make. But this is a BUSINESS. And you have to look out for yourself. So be prepared to do so before you start looking for an agent and you'll do much better in the long run.