300
What happens when you follow more than 300 people? How does the dashboard know who to stop showing? Does he start from the back or the front?
Overfollowing Tumblrs like myself need to know.
The current limit is 400. We increase it every so often as our infrastructure grows to support it.
The Dashboard posts-of-friends fetch hits Tumblr’s database architecture harder than anything else in the service — and it gets hit a lot. We currently can’t afford to remove this limit.
As for which 400 people it chooses if you follow more than that, it’s undefined. There’s no ORDER BY in that query. It will probably include the most-recent 400, but that can’t be guaranteed every time, especially as we make changes and optimize that feature.
