In addition to adding some nice speed and interface enhancements (like swiping up to check for mail), our favourite Mac Gmail client Sparrow (which works great with IMAP, too) has decided to take a stand against email attachments.
Now you can log in with your CloudApp account (or sign up for a free one) and use that service for attachments instead. Once enabled, when you drag a file onto the main area of an email message it will automatically upload to CloudApp and place a link in the message. A sound will play when the upload is complete, but you can turn that off. If you feel like attaching a file the traditional way you still can by simply dragging it to the bottom of the message rather than into the body. This way you can use the method you prefer when sending files. Pretty neat!
Note: When updating to version 1.4, it'll take a minute to migrate your old mailboxes. If you have many it could take a bit longer. It's not a huge wait, but you may not want to run the update when you're in a hurry.
CloudApp in Sparrow [Sparrow Support Blog]