This is definitely a positive as it makes for a cozy and trusting environment, whether it be for work projects or parties. But a network is like a garden. It must be tended and cannot simply be left after a great beginning.
There is the concept, most championed by Stephen Mansfield, of the "band of brothers" (or sisters, as it may be) who you can consult on every issue you run into. While this builds a recurring loop of absolute trust, the reality is that even the most curated band of brothers is going to have some gaps in specialties and expertise. Thus, it makes sense to go into your network and build teams to solve particular personal or professional problems that fall outside the areas of expertise of your trusted inner circle.
How can you tell if your network is too dense? Make a list of the ten most important people in your network -- your "go-to" people. After that, go through each person on the list and find out how many of those people would list one of your ten on their respective lists. If none of them would, this is a bad sign, as it means you're not bringing together enough of the people you already know. If more than five of them would, it means your network is too dense. This can lead to drawbacks like:
- lack of creative thinking (hard to escape the echo chamber)
- hesitance to go outside of the circle for resources (if there's a graphic designer in the circle, it may be awkward to ask to pursue work with a different person)
Remember that if you have a dense network, it means that you've done a great job of building a group of trusted individuals and introducing them to each other. But remember that what got you there was openness to meeting people in every context and then offering value and introducing them whenever possible. There's no reason to stop doing that. That's how you can keep leaving everything better than you found it.