Yes those who have username accounts but no blog can become followers and click the "like" button. And there have been cases of "like" button spammers but we cannot remove their bogus "likes".
There are several different ways that readers can start following your blog.
Your blog followers is the sum of the following:
- WordPress.com blog followers
- Any followers from connected Publicize services (Facebook, Twitter, Messenger Connect, Yahoo!, or LinkedIn), which you can check in Settings -> Sharing
Go to your site stats page and click Totals, Followers & Shares
Click the Blog link under the number and the Site Stats » My Followers page will open. Click the Email Followers link.
A follower can click the “like” button without visiting your blog and creating a page view stat.
- A follower can click the “like” button when viewing your posts in the Readomatic reader on the home page of WordPress.com
- A follower can click the “like” button when viewing your posts on the Topics pages.
- A follower can click the “like” button when viewing your posts when using an app.
- An email subscriber can click the “like” button in the email they receive of your new posts without visiting your blog.
P.S. To compel readers to click into my blog to read the full post I have set my RSS Feed to “summary” on this page > Settings > Reading