New information has surfaced about how Yahoo was roped into complying with mass surveillance programs. In the past Yahoo has characterized themselves as champions of privacy, saying that they tried to legally fight Prism and other surveillance programs in secret court.
The new evidence presented by the Guardian supports the claim that Yahoo actually fought mass-surveillance and felt that the court orders that it has received were overly broad, and not legal due to a failure to go through the correct channels to get the orders authorized to be executed.
They challenged the US government in a secret court known as FISC (the Foreign Intelligence Surveillance Court). Since the Snowden revelations, Yahoo has been fighting legally to get the details of the FISC decision made public record, so the public will be able to see the arguments made and how the final decision shook out. Yahoo lost the court fight, and a subsequent appeal.
During the trial Yahoo was threatened with fines of $250,000 per day for non-compliance with the court orders to hand over data, and those fines were set to double every week.