Is EXIF data stripped by iOS and/or Twitter on Tweets with images?

From the Twitter Help Center:

What happens to the Exif data? I heard there are privacy concerns there.

We remove the Exif data on upload. It is not available to any consumers of your image.

Just found Social Media sites: photo metadata test results which tested various sites, including Facebook, Twitter and Google+. An excerpt from their site says:

We have uploaded a test image with embedded metadata and have checked if any of the embedded values are displayed and if so, which ones. As a next step we have tried to save the picture from a Social Media web site or system on our computer and then we checked what metadata fields are still embedded.

The Twitter test results (as of March 2013) are:

No metadata shown, all embedded metadata stripped-off from image files.