There is not the corresponding selling pressure on bitstamp.
Have you analyzed the most recent price movements at Gox? Looks like they fall under the large buy orders from whales category.
Here's the results for today:
2013-08-21 00:04:42 UTC: (462 ts in 17s) 3471.65 @ 123.29 BUY (min: 122.34, max: 124.45) big ts: ["249.98","199.15","167.00","138.50"]
2013-08-21 01:54:53 UTC: (78 ts in 4s) 680.50 @ 124.50 BUY (min: 123.49, max: 124.70) big ts: ["166.43","115.05","72.97","43.00"]
2013-08-21 02:50:27 UTC: (36 ts in 1s) 1088.79 @ 124.90 BUY (min: 124.83, max: 124.91) big ts: ["497.85","300.00","49.75","40.00"]
2013-08-21 03:36:44 UTC: (129 ts in 6s) 1000.00 @ 121.68 SELL (min: 121.00, max: 123.04) big ts: ["140.54","124.78","112.42","69.60"]
2013-08-21 04:49:13 UTC: (95 ts in 4s) 490.00 @ 120.40 SELL (min: 120.00, max: 121.00) big ts: ["40.00","40.00","39.00","30.00"]
2013-08-21 13:27:46 UTC: (94 ts in 4s) 868.91 @ 120.23 SELL (min: 120.00, max: 121.48) big ts: ["100.00","98.00","91.65","83.33"]
2013-08-21 14:38:38 UTC: (78 ts in 4s) 1000.00 @ 121.71 BUY (min: 120.43, max: 122.50) big ts: ["100.00","100.00","65.94","60.00"]
2013-08-21 14:39:36 UTC: (146 ts in 6s) 1000.00 @ 123.32 BUY (min: 120.55, max: 123.99) big ts: ["175.51","132.73","90.00","43.12"]
2013-08-21 16:06:39 UTC: (152 ts in 5s) 1000.00 @ 123.57 BUY (min: 121.01, max: 124.23) big ts: ["133.33","60.00","46.00","40.00"]
2013-08-21 16:07:29 UTC: (225 ts in 8s) 2404.00 @ 124.75 BUY (min: 123.40, max: 125.00) big ts: ["401.16","173.58","102.18","101.00"]
2013-08-21 18:06:17 UTC: (108 ts in 4s) 1021.96 @ 124.39 BUY (min: 122.93, max: 124.91) big ts: ["250.00","71.19","60.79","40.00"]
2013-08-21 18:46:40 UTC: (44 ts in 2s) 444.98 @ 124.21 BUY (min: 123.00, max: 124.90) big ts: ["57.00","50.00","50.00","40.00"]
Again, we have several very obvious exact 1k orders. And a few even bigger. For example, the 2404 BTC one had probably limit price of 125 and exhausted the order book.
Interestingly, today we had more big sells. But still, the buys dominate.
Whales are buying BTC in large quantities to move out of Gox. They don't necessarily need to cash out immediately. They could be holding BTC for speculative purposes as there is no other exchange that could possibly handle that volume (neither can Gox, that's why the price has moved so dramatically).
This is quite obvious when you see such large buy orders in 1 minute time spans vs a gradual move up in price.