Funny, I'm having this same conversation about membership "requirements" with several other people this week, so let's see what happens here.
I kind of think there are 2 (mostly) separate issues in this sort of conversation:
1) the importance of going to church, and of reaching out to people who aren't in church and finding out what's going on that they stopped coming and encouraging them to come back
2) what the requirements should be for someone to be able to vote
It seems to me that the requirements for who can vote should be fairly strict - it's a decision of the community, for the community, whether you're voting to call a new pastor, approve a budget, or change denominational affiliations. Now clearly, if you've got some job that requires you to work on Sunday mornings, there's grace for that, if your kids are still coming to Sunday School and you're on a committee or two and you send in a check and come to midweek worship if/when it's available, etc...
But if you've donated $10 in the last ten years and show up on Christmas most years - when the weather's not too bad - and you are really in no discernible fashion a member of the community other than that you show up once a year when it's guaranteed to make you feel warm and fuzzy inside or because Grandma would flip out if we didn't go to church on Easter, are you really part of the community? Should you really be given a voice in determining the direction of the community?
Somewhat tangentially, I'm unclear where this whole "I don't have to go to church to be a Christian" thing comes from. Can you imagine anyone saying that in the 3rd century and getting away with it? Does it seem like that's something Paul (or hey, Jesus!) would be down with? Those two strike me as people who thought you were either in or out, and they didn't really have time for people who just wanted to screw around on the edges for decades at a time...