Whenever people sign-up to my blog generally I get notification emails. But recent days my blog followers number went up to 230 (There were 45 followers two weeks back). How this can be? I didn’t even get any email notification to my inbox.
The WordPress.com members who are following your blog will be notified by however they’ve chosen to be notified, either by email or in the WordPress.com Reader.
If you’ve connected your blog to your Twitter account with Publicize, then your new post is automatically pinged to your Twitter account when you post.
I just had a look at my personal blog’s stats and suddenly I have a huge number of followers and I believe it is as iphonist1 said above, that it is Twitter followers (which is why you would not have received notice by email of new followers) plus your WordPress.com followers.