When viewing Server Fault on my iPhone, I'm seeing some questions highlighted as if they are my favourite tags, but... they're not.
Here's another example, on Meta:
Switching back to the mobile view fixed the problem briefly in this case, but then the highlighting came back.
The page appears to be coming back with the right user information, suggesting the problem is not inappropriate caching at the ISP level...
...despite incorrect highlighting being applied due to someone else's (or a random) list of favorite tags being specified later on in the page: