With the rapid expansion of the internet and electronic communication, it is easy to feel as though the world we live in is much more transparent than 30 years ago. Yet with alarming frequency, things are revealed that were hidden from the public by the government, things that we feel we should have been privvy to at the time. It's not so much an issue of can it happen, but rather how often does it really happen.
Unfortunately, when governments and powerful entities do not want unpleasant news stories released to the public, they can find means to cover-up these stories. Yes, the internet does make it easier to get news stories to the public. However, powerful officials can still find ways to keep these stories from coming to light. In short, yes, a cover-up like the one involving British eggs tainted with salmonella could still occur today.
Any government, at any time, has the power to keep a story under wraps by simply saying it's in the interest of national security. So, could this happen again? Most certainly! Will it? Most certainly. It might not be eggs, it might be whether or not there's WMDs on native soil, or that hormones in the food we eat is killing us in the long term, or even that genetically modified seeds are a means to control population. But yes, a coverup is most definitely going to happen again.
The British egg salmonella controversy from the 1980s gained new life in the early 2000s when it was discovered that Edwina Currie, the politician who started it all, was right about her accusations - but that the truth about salmonella-poisoned eggs had been kept quiet. This is nothing new, and I wouldn't be surprised if we found out something similar was happening now. Companies and countries alike always want to either debunk or silence allegations that their products or policies are not safe.