The What's Happening? page, or MTGOnline.com, is the primary source of all Magic Online news and decklists, directly from Wizards of the Coast. Until recently, they published winning decklists from all online events, including Daily Events, Premier Events, and online Pro Tour Qualifiers.
On October 17th, a Wizards forum user noticed and posted about the gradual disappearance of Daily Event decklist information, which prompted a response by Wizards Community Coordinator, Sean Gibbons, on October 26th. What was initially thought to be a bug was revealed to be a policy change.
The quote from Gibbons can be seen below:
"In regards to the recent reduced event coverage, this was a conscious decision by the Wizards R&D team that wasn't made lightly. Ultimately, we feel that publishing every deck list leads to solving constructed formats far too efficiently, resulting in early stagnation that's not fun for anybody. We still want to show new deck ideas every day and provide insight into the Magic play environment, but we don't want metagame development to become purely a function of data analysis. Going forward, we'll still provide the winning deck lists from all Premier Event top 8's. We will also show the 4-0 and 3-1 deck lists for one completed Daily Event in each format per day."
In brief, a decision by Wizards of the Coast R&D was made to limit the amount of Magic Online decklist information to be released to the public in order to slow the speed with which formats are solved.