I must be living under a stone. This is the first I've ever heard of black balloons for 5oth birthdays. What the....??? Who came up with that bizarre concept?

I had two birthday parties when I was a kid- my 4th and my 5th birthdays.
Nothing after that. I finally had to ASK DH for us to throw a birthday party for me last year on my 54th birthday. It was a great party with about 30 friends ('no gifts' was specified) and a wonderful banjo cake, and I felt very happy having had the party.
It's funny, because all my grown friends are always having birthday parties and throwing them for each other. Go figure. At least I had my one great memorable party last year.

Personally, I think it's somewhat pointless for 20 or more people working in an office to be throwing birthday parties for each other year after year. What an ordeal that would be! I'd think a card and maybe a song would be fine.