It is not uncommon these days for younger people to spend an hour or more a day online, and although this does detract from time spent taking to family members, it is not necessarily affecting their social development as will now be discussed.
The primary reason to disagree with the statement is that a considerable amount of time that youngsters are on the internet is actually spent on social networking sites such as Facebook. As these sites are specifically designed for social purposes, the argument that social skills are declining would appear to be invalid. It is only when the time online is spent playing single player games or generally surfing for entertainment without interacting with others online that this could be considered unsociable.
In addition, an increasing dependence on the internet for a broad range of tasks from completing homework and studies to checking bank balances and searching for employment means that being online is often simply an alternative manner of working or completing necessary chores, and should not be considered related to social skills at all.
Admittedly, if too much time is spent online playing games or looking at websites, then there is the potential for surfers to become less able to interact with people directly. However, this can be negated by ensuring that time online is limited to a reasonable amount, and can even be controlled by using technology that actively records the amount of time online.
To sum up, it is not that the internet is causing us to become less sociable, it is simply that the nature of social interaction is changing.