I like to think of it as the 'Trojan Horse" rule - where you send an innocent looking electorate MP to parliament, and then a bunch of list MPs sneak out of them when you're not looking!

Anyway, under MMP there are many other of situations where some voters are given more power than others. For example;
- Maori party voters got to send some extra labour MPs to parliament as overhangers. ;)
- 121 voters get to decide amongst themselves who forms the government, and those same voters (sans the speaker and the opposition) get to decide what all of our laws should be.
- And that's assuming that the 1 voter with an overriding vote doesn't veto any of them!

PS: Had you genuinely never heard people complaining that voters in Epsom (or Tauranga, or Coromandel) were given too much power because of this rule? I'd thought that was the main objection to it!