Hostels are definitely the place for socializing. Since the guests in a hostel are mostly younger people, there are plenty of occasions to get to know other travellers. Some hostels organize parties, meetings or competitions, or have a bar within or just outside their premises where people can meet and chat to fellow guests.
Hostellers are generally more interested in meeting other people than your average tourist, so it's much easier to get in touch with them, share common interests and exchange advice, tips, etc. Many people travel on their own all over a country or continent more than a year long, and rely on chance meetings to make friends.
Remember: you can always meet people who have opinions (on politics, sex, religion, your country) that are very different from your own, so you must be prepared to be tolerant and understanding other people's positions and views on life. Without a doubt, this will certainly enrich you and broaden your perspective. So if you go to a hostel, expect to meet new friends, (especially if you speak some languages) and put on your best smiling face. Who knows, you might make the best friendships of your life!