The method is as effective as a dead cow is at mooing.
The list in your Options dialog is a very simple "trick". MSN Messenger has a list called the "RL", on which people are stored that have you on their list. It serves little purpose other than contact list management for the client itself (and you could detect "ghost contacts", contacts that you have on your list but not vice versa). This is however far from "block checking" seeing as they might still have you on their AL and hence, you still see them online & can talk to them.
No block checker utility is 100% effective anymore. Every block checking method suggested so far as flaws. One more than others. Nowadays every block checker has a couple (read: a lot) of conditions that need to be met in order to check if someone has blocked you (e.g. Allow others option). Here's a pretty complicated one, that a) assumes person is using 7.x, b) has "has signed in" alerts enabled: Set status to HDN, change DP, sign in. If the person opens a conversation and requests your new DP within the time the alert is being shown on their screen then they don't have you blocked. You could, if you want, change your friendly name as well to something more attractive to click (this is called "Toasting").
Anyhow, we don't need a gazillion block checkers, if you want to find out, just send and e-mail or call the person. You know, IM isn't everything. Besides, there must be a good reason youve been blocked. Unless someone finds a truely effective method I suggest topics like there are just ignored or something. As an example,
http://msnblockchecker.com used to offer a trojan invested block "checker", you willing to risk your computers security for simply checking if someone blocked you? Think not.
In short, don't bother
Block Checker that works (idea)
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