I know from reading this:
That there wasn't a limit to the size of an application that could be downloaded over the air (OTA) but I wonder if a limit, like that imposed by the Apple App Store (20MB) exists now that the Nexus one is running on AT&T's 3G network as of today.
Thanks in advance for your help/
Truk
Nope. Not that I've read/seen in the Google Help on Uploading Applications etc.
Then I dug a little deeper on this and found this link in which Dianne Hackborn mentions the following:
The Java heap is limited to 16MB, but that is just the heap, so I don't believe code is included.
The basic answer is: keep your app as small as possible. A little more detail: the G1 has ~75MB of storage for both apps and data, so if your app is ~5MB it is using 7.5% of that storage which is getting quite noticeable. Also the code needs to be copied out during the dexopt phase, so if your size is significantly related to code than that total space needed is likewise increased.
At that point, it's just a matter for you to decide how much space your application can take before your users won't think it is worth keeping on their phone.
So, actual limit? Sort of but not really. Practical limit? Absolutely.
To bring this current, and since you've tagged Nexus in here, a Nexus One has 512 MB of flash memory on board and of that 190 MB are available for loading applications.
No real limit, but because mobile phones haven't much memory, keep your application as little as you can.
Plus, if your application is heavy, it will take time and bandwith to download. Your users may be discouraged by that.