Great idea for a plugin but it doesn't appear that it is working. I installed and activated the plugin and then logged out as admin, then logged in as test1 which is a subscriber in browser one. Then in another browser lets call it browser two, I logged in as test2 which is also a subscriber. Then in browser one, test1 goes to the members directory and blocks test2. Test2 then disappears off of test1's members directory. Then in browser two, on test2's members directory test1 is still visible, when test2 clicks on test1, test2 is taken to test1's personal activity, then test2 clicks test1's profile tab and test2 is taken to test1's profile. Basically the plugin is ineffective! I understand this is in beta but I would never tag a beta plugin as 1.0 it would be more appropriate to name it 0.10 or something to that effect. Also your repository is a mess. You have an assets folder inside of your trunk. That folder shouldn't even be there. The items in that assets folder belong in the assets directory of your repository. Because of this people who download your plugin are also downloading the assets which is unnecessary and only bloats the plugin. Also because of this your screenshots are not showing up on the plugins page. I hope you can eventually get this plugin working and I would also like to see it block items from the activity stream as well. Please don't take this as negative, I just wanted to make you aware. Good luck!
Edit: I am using latest version of WP/BP and bp-default theme. No other plugins or custom code as it is a fresh install.