Do personal emails work?

The campaigns of Obama and McCain both think I am an undecided voter in Ohio, though if anyone checks my zip code I live on an industrial estate. But it means I am happily receiving their e-newsletters and campaign emails. McCain's team are fairly infrequent in sending things and often it is more a series of news links than the mobilisation attempts employed by Obama. The latters' email campaign actually seems to hinge on personal emails from him, his wife, David Plouffe his campaign manager and since the Democratic convention Joe Biden joined the emaillers. Joe has sent an email today about his wife, the text is as follows:

"My wife Jill is an extraordinary woman. Jill's passion has always been education, and even during the campaign she's been teaching class during the week and joining me on the trail on the weekends. But this week, she also found some time to go to campaign headquarters and call voters in crucial battleground states. Jill has always had a great time talking to potential supporters, and I'm sure her calls brought Barack and me a few votes closer to victory. Can you do the same?"

Receivers can then watch a video of his wife Mrs Jill Biden phone canvassing, well mostly actually talking about herself and are then told the importance of the activity. But why is this tactic employed?

The notion to personalisation is to build a relationship between the individuals and so it draws on the same set of motivations as face-to-face communication between friends, not necessarily close friends but at the very least fellow community members perhaps. The question for me with it is whether it works. While the receivers have been introduced to new characters as the campaign has progressed towards the election are US subscribers now becoming anaesthetised to these appeals as they know what they are going to ask? It seems to have been used repeatedly and almost on a daily basis if not more often, what is the saturation point for any 'neighbour' asking for more participation - be it time or money - while the tactic is said to be successful is there a point where anything becomes over used?