I have used Yoast for years and have never seen an anonymous “Subscribe” box on any of my sites’ dashboards. Even in places where Yoast (and other plugins) request user information, it’s clear what is being requested and why.
Your “Subscribe” box, on the other hand, did not mention:
– Who was asking for the information
– Where the information was being used
– What the user is subscribing to
– The plugin that was responsible for the subscribe button
There was also:
– No privacy policy
– No mention or reference to Safe Harbor policies required by the US and EU when soliciting personal information
You’re can do whatever you want with your free plugin, but as a member of the WordPress community, it’s my responsibility to warn people away from anything I notice that may be dangerous.
At best, this is poor design and planning. At worst, it’s deceptive and potentially malicious.