As some people might know, adding share buttons from Facebook and Twitter can cause a page to slow down. I've seen many sites pass on the common iframe implementations that these sites offer and simply create icons that link to a sharer url for better control of page performance. http://www.facebook.com/sharer/sharer.php?u=http%3A%2F%2Fwww.cnn.com%2F&t=CNN%26s+website%27
However, I've also read that Facebook is dropping support for these links. For example, this link now redirects to the Like Button. http://www.facebook.com/facebook-widgets/share.php
Here is an article noting that Facebook is deprecating/has deprecated it's share functionality and is sticking with the Like button. http://www.barbariangroup.com/posts/7544-the_facebook_share_button_has_been_deprecated_called_it
I'm assuming this is the same for the sharing url.
If the sharer url is no longer a reliable option, what other methods are there besides using 3rd party widgets (like Addthis)?