I've found when people ask this question, it's usually because they don't have a network to ask. Or, right or wrong, they just don't like the social aspect of going to their friends for work.
To be fair, there's a good argument for never mixing friends and business. You wouldn't want a project that goes wrong (which is a risk of doing business and somewhat expected and budgeted for on both sides) to jeopardize an friendship, and similarly you wouldn't want someone exploiting your friendship to get an unfair advantage in business (that they will often not reciprocate if the situation was reversed).
Well there are friends and friends and yes the categories merge. But since grad school interviews every job I've gotten has been through people I was friendly with professionally.
from one tech friend i learned this, after a failed project of his that cost him a friendship: make friends through business, but don't do business with friends.
