List variables are great, but they are not as user friendly as they can and should be. I was really excited when they first came out, mainly to use them for internal campaigns. I would be able to get impressions and clicks all in one variable. I would set all of the internal campaign impressions with an impression event on one page, and then if the user clicked through one of them, it would take over and receive credit for any downstream conversions.
However, the whole "full allocation" is what throws me off. If I set values A, B, and C on page 1 with event1 (impressions), and then C again on page 2 with event2 (click through), it will give a count of event2 to A, B, and C instead of just event2. It would be great to have a "most recent" allocation to only give credit to last value(s) passed. So in the example above, C would be the only one to get a count for event1. Of course there are some other implications to doing this, such as overwriting this with a new impression, and that is fine and can be dealt with separately, but it would be really great to have "most recent" allocation instead of treating it as an array and appending the values to a big list during the expiration period.