Sorry to hear that you didn't hear back as to whether you got the job or not mate, I know how you feel. The same has happened to me more than once as well, both of the job interviews that I attended went rather smoothly - I was fed with the "We're looking to get the ball rolling really quickly and therefore we want the right person to start next week, you're up against someone else who we are interviewing tomorrow morning and we will definitely let you know by the end of tomorrow, even if we turn you down"
Next day - absolutely nothing. With one of them positions I even chased them up a couple of days later and the lady at their HR department said that they were still conducting interviews apparently and that I was on the list for them to call back when they had done, another 2 days later - still nothing.
These cretins really know how to get your hopes up by feeding you with false information and lies - it really ***** me off. From personal experience now, if one gets the job then the employer usually rings them up within 2-3 hours after conducting the interview. A temp job that I had last year which was for a massive firm literally told me that I got the job within half an hour via phone after finishing the interview. Maybe though for you OP, because it was a Friday they may of discussed amongst themselves who to offer the job to and they have decided to wait until Monday to notify the lucky person. So if you don't hear anything back by Monday, then I would take it as a no.
Liam