It generally does not hurt to be able to chit-chat before getting down to business for a business meeting. However, I'm not a great believer in finding business at bars.

Ultimately it comes down to awareness. Each person you meet might be a potential customer. How important your social network is in your business might be affected by the nature of your business.

Social contacts can be a great source of good business without doubt. I'm not sure that it should be the corner stone of your marketing strategy, though.