I still wish phone manufacturers would take this "world's slimmest technology", and then build a phone that's a regular thickness only with 3x the battery life.
http://arstechnica.com/gadgets/news/2012/01/motorola-release...
For peeps younger than me: http://en.wikipedia.org/wiki/Motorola_MicroTAC
Nevertheless, I think that the problem with current smartphone batteries is that the leap from a day of use to a little more than one day loses the convenience of charging it at home at night.
For example, I'm used to charge my iPhone at night in my bedside, and the iPhone lasts about a working-day of charge.
A battery that lasted 1.5 days would not be as useful, because the battery would probably drain somewhere where having access to the battery charger is not as convenient as the one plugged at your bedside.
A battery that lasted "1.5 days" might actually last a full day of heavy use, such as during travel. That's my biggest complaint about battery life with smartphones. They will generally last a full day on a charge, as long as you aren't using it often.
It's possible that with 2 pound laptops and 5 oz phones, we already have almost ideal form factors given the constraints of normal usage. At this point, making a lighter phone is like making a lighter pencil or book - more novel than desirable.