A number of hostel managers have commented to me that, yes, it does have a negative effect.
Many travellers, quite reasonably, need to spend SOME time on a hostel evening on computer, whether it is their laptop using wifi, a fixed computer provided by the hostel, or (if neither is available) an internet centre in town.
If the common room is occupied by people all using computers, the social life will indeed suffer. Even if you use one for half an hour then take a break, everyone else will do the same at different times so no one will look as if they want to talk.
At least you do not have to join in with someone's computing, and you can do your own thing, such as read. TV has the same effect, but worse because you are effectively forced to watch whatever programme the TV watcher has chosen.
With 2 different hostels in Launceston in mind, I suggest that: There should be one common room, perhaps attached to the kitchen, where TV and computing are outlawed. If people SEE that there is good social interaction going on, they will be attracted there, and will go there when they have had enough computing or TV. If the hostel is large enough, it can have a TV room and a computing area elsewhere, and all can be satisfied. But trying to make one room into social plus laptop plus TV is a dead loss.