Most people usually rely on a simple notebook to keep track of group expenses like the ones they split with their room mates. Now if there are just two guys in the group, a notebook might suffice. But when that number goes higher, things start getting complicated.
There is one advantage notebook has when it comes to tracking bills, especially if you are using it for tracking your apartment bills. You paid for some bill or bought groceries for the house, you can just walk into your apartment pick up the notebook and make an entry. Doesn't take too much of time or effort. But something we realized from our own personal experience is the time saved at that moment comes with a debt. A debt that we need to repay on some weekend sitting together for hours figuring out who owes whom how much, not exactly a fun thing to do especially on a weekend.
On Beezang, you can enter bills on the website or via twitter or by sending a simple email. Beezang while retaining the simplicity of entering bills also does the maths for you. Moreover you can use it to keep everyone on the group updated about the latest bills and settle up easily when the time comes.