Although the site's functionality for end-users has been fairly stable on Friday after a lengthy outage Thursday, that's not the case for third-party applications that use the Twitter API (application programming interface).

Twitter acknowledged on Friday afternoon that some of the defensive measures it has taken to deal with the attack have negatively impacted third-party applications and thus the developers who created them.

, which provides productivity tools to more than 100,000 Twitter users, came to a "virtual standstill" on Thursday and was operating in a scaled-back mode on Friday.

"We had to pause all Twitter account automation processes, and at time of writing those processes are still paused because the API is still actively refusing high-volume API calls," TweetLater owner Dewald Pretorius said via e-mail. "Our service makes in excess of 40 API calls per second, 24 by 7, during normal operations, and Twitter is still not allowing that type of volume while they are recovering from the attack."

Twitter could have done a much better job of communicating with the developer community, said Andrew Badera, president and CEO of , an IT consulting and software development company that has built several Twitter applications.