The default of 3MB may need to be reconsidered - the decision made some 7 months ago.
@codinghorror's example phone a Nexus 5 was released November 2013 was perhaps quite out of date at the time of the decision
with an 8 MP, 3264 x 2448 pixels camera.
A contract phone in the UK is a "Samsung Galaxy Alpha" released September 2014
with an 12MP, 4608 x 2592 pixels camera.
I don't have any average image file sizes to offer but the sample I have been sent is 3.2MB
(the user was unable to upload it).
In addition the 4th most popular camera phone (for uploading photos to flickr) is the 16 MP, 5312 x 2988 pixels Samsung Galaxy S5 released April 2014.
I took a sample of the first 15 images on Flickr in a "Samsung S5" search that the following characteristics:
- Taken with a Samsung S5 model
- The "Original" file was downloadable
- Was not a panorama image
- Did not appear edited
- Had original EXIF data
- Was not a picture of the phone itself
The file sizes:
This was just a quick analysis - perhaps flawed - but a ~7MB average leaves me with a bad taste.
I submit that optimizing images before upload and default upload file size limit might have to be reviewed.
And that an average size might not be right and that we have to remember to aim slightly higher with limits to prevent user issues and support requests.