Having free alcohol around is fine; you don't see much day drinking (social decorum works well here), and it means people tend to stick around a little on fridays to chat instead of taking off immediately. Some employees, anyway.

However, there are other cultures where it's a huge smell for, umm, fratty culture. Don't ignore your gut on this unless you like cleaning up your boss's puke and feeling a stigma for staying dry. I've also experienced this and it was really fun for a small startup where everyone is friends—it needs to be carefully managed as you grow; you lose employees this way.