If you work in a small office, like MHLI, co-worker birthdays offer a nice break from the routine. We usually go out to lunch as an office and everyone chips in. Whoevers birthday it is might decide to pick up some cupcakes or bagels to celebrate. If we are feeling festive, someone might come in to the office early and do a little desk decorating.
If you work in a larger office environment, birthdays may be such a regular occurrence that someone implemented a birthday celebration policy. Once a month communal birthdays are common.
It reminds me of the Seinfeld episode where Elaine’s office was celebrating so many office birthdays (and anniversaries and sick days) with a cake that she started craving the afternoon sugar rush. http://www.youtube.com/watch?v=LAcOjQKz_Zc
If you do a quick internet search about office birthdays, you will find a lot of opinions. Birthdays and other milestones can be seen as a small way for the team to bond outside of the regular workday parameters. If can also be a way to make the more socially awkward nervous or even to breed discontent.
Does your office allow people to “opt-out” of birthday fun? Do you love or hate office birthdays? http://www.youtube.com/watch?v=_IbgTPftvWc