[pavel_lishin]

Hypothetical example: When I open Twitter in the browser, I see a feed - but I also see a "What's Happening" section, and a "Who To Follow" list of suggestions, as well as what looks to be my inbox, minimized. Plus, the feed itself automatically loads the images that people are tweeting.

If you know a client is likely to be from a place where bandwidth is expensive, you may choose not to load the "What's Happening"/"Who To Follow", or the messages, or possibly even the image URLs (which I'd guess come from the backend with an array of URLs of those images in various sizes & resolutions.)

Hell, you might even load a smaller subset of the feed - 10 items instead of 30.