One of the principals of the tease is to keep viewers sticking around, to simply give them a taste of what's coming up later in the newscast. If you give away the entire story, there's no reason for anyone to stick around.
But with the growth of the internet, we now have a new problem. How much do you "give away" on the net before your newscast?
Years ago, when crews used two-way radios to communicate, we'd have our scanner tuned into the frequency used by the competing stations, and they did the same. Every once in awhile someone would slip up and give away a story, and if you had time you could jump on it.
The same is true when using the internet. Stations routinely monitor the competition, and if you give away too much, two bad things will happen; you'll lose your story to the competition, and viewers won't have any reason to tune in for your newscast. If it's breaking news that everyone has, you can give away a little more, but if you're working an exclusive, it's dangerous to even hint at what you're doing. Many stations do not post anything on the net until a story has aired.
While people have come to expect everything on the internet, the net still aint paying the bills. You still have to drive people to the television sets, because your newscast is still your bread and butter.
The principles of a good tease apply to the internet. Whet the viewer's appetite for more without giving away what you're doing to the competition.