When creating Twitter Apps. Most apps, will hotlink Twitter profile photos. But if a page is displaying several 20-40 profile image photos. Firebug (network tab) reports all these photos taking up 30-50 ms (each) to load. Sum that all up, and you get a few seconds.
For page rendering and optimization purposes. Should Twitter profile photos be cached/stored on the local server?
On a side-note. I understand the challenges of outdated photos (since they will be cached). But that isn't the point right now.