Why is my build file size so big?

I am using Unity 3.5.6f4 and building to Android. The final apk size is 66.5 MB, yet in the editor log, it is showing a complete size of only 30.8 MB:

Textures 22.2 mb 72.2%

Meshes 280.8 kb 0.9%

Animations 0.0 kb 0.0%

Sounds 1.7 mb 5.5%

Shaders 89.7 kb 0.3%

Other Assets 1.9 mb 6.1%

Levels 294.7 kb 0.9%

Scripts 205.6 kb 0.7%

Included DLLs 3.8 mb 12.3%

File headers 317.0 kb 1.0%

Complete size 30.8 mb 100.0%

What could be causing the file size to be more than twice the size it says in the editor log?

For comparison, my last project had a complete size of 325 MB, yet the apk was only 24.MB. Why the huge discrepancy?

Thanks for your help!

Well Unity itself takes a decent amount of space - depends on whether you have Pro and Bytecode stripping turned on etc - if not then the cost of the .NET libraries you use plus any native plugins will be added to that size in their entirety, otherwise some code will be removed. In addition there will be the size of your splash screens etc and all of your streaming assets.