I, personally, would recommend starting on acoustic. I did, and I think the benefits far out weigh the downfalls. As stated previously, the main benefit is that you develop more dexterity and strength. The biggest thing that I took away from the acoustic is that it forces you to learn how to play cleanly and accurately. With an electric you can always hide behind distortion. The acoustic is the purest form of guitar. It's guitar playing in it's metaphorical birth day suit.

I think it helps build the all important discipline that it takes to approach the guitar seriously. That's my opinion though... and in no way do I expect it to heavily dictate your decision. It's your choice in the end.

Rock on!