BitMinter has had way more than 3 in the last 1600.  I'm curious now what they use to differentiate between "stale" and "orphan" considering those mean the same thing when it comes to blocks.  They've had 3 stale+orphan in the last 100, 5 in the last 200, 7 in the last 300.

Smaller pools will have more orphans than larger ones purely because they're less likely to be able to confirm their own orphaned block than a large pool.  It's also very common to see random events (1 in 100) show up in clusters, meaning a small sample size can show a much larger (like the 3/100, 5/200, 7/300), or smaller (0/300) occurrence just due to the distribution of random events.


UPDATE:  Guild has had 4 orphans in its last 600 blocks, 7 in the last 850.  That's not far off from the approximation of 1%, which is what has been estimated by most pools for years.