The author said he looked at both the New York Times and Washington Post to see how easy it was to link stories to Twitter accounts. He found that the New York Times made it really easy by compressing the length of the link in a bit.ly address. Using this shorter form, users could pull the link and still have enough characters to comment on the content of the article. However, the Washington Post didn't foresee this issue with long URLs, making it a whole lot harder to post links from the Post to a Twitter account and have room left to "retweet" the article. Readers would either have no characters left or would have to go through a convoluted process to compress the length of the link themselves.
The author also noticed (and it's easy to double check, just click to both sites) it's also a lot easier to find the "Share" button on the Times website (right next to the headline). The Post only puts its sharing buttons at the end of the article, after the "Sponsored Links" ads. Most readers probably won't bother linking if they can't find the button easily, and the Post makes it quite a scavenger hunt.
The Post gets points for including the option to link to their story, but it loses a whole lot more points by making it impractical for readers to actually do the sharing. If it's difficult to use, it's almost not worth it to attempt having web-sharing tools because it makes readers think you're not actually as tech savvy as you think you are... And that doesn't reflect well on the future of an organization in a new media world, does it?