Do not use your ezine in the same way as you would Twitter or a blog. Your subscribers have given you permission to send them information, but, if you abuse it, they will soon be sorry they did. The result will be that they will leave your list just as quickly as they subscribed to it. Send updates once or twice a month and leave it at that.
For lots of advice and free tips, check out the FREEBIES page at the VA Success Group