I did actually:
https://getsatisfaction.com/battlefield3/topics/server_browser_filter_and_custom_servers_not_working_right_not_displaying_custom_servers
They think it's not a problem, people just shouldn't be stupid. -.-
To clarify: On the server browser there's the "Advanced settings" area which let's you set various custom filters.
The problem is, that if any of those adv. filters are active and you happen to have a preset (normal, hardcore, inf-only) activated, too, you won't find any servers at all.
Some people - including me - think that this isn't obvious enough. That's why i'm proposing it here: if "Filters" is checked under "Advanced settings", automatically de-select all of the "Presets".