Everyone is focusing on the outrage. Arseblog has a particularly emotional response and I don't blame him. But it borders on Tea Bagger conspiracy.
We can debate whether it was a malicious tackle and I have seen it and there is no conclusive proof that it was one. Shawcross did not come flying in with studs up and extended leg. Was there a pattern of chopping down players prior to that? I saw Darren Fletcher do a lot dirtier in the Man Utd match at OT.
There are a lot more factors in operation than simple malice.
Three players in four years is an eye catching statistic but it is also true that 2004 and after, Wenger went younger and built his teams around speed. A rapidly mobilizing team that has buried the George Graham days for good.
With that came a certain diminution in size and physicality. We have grown quite a bit smaller. The average height for the 2004 starters was a little over 6' with only Ashley Cole and Freddie Ljungberg below that threshold. It is a bit startling to realize that Bergkamp, Edu, and Pires at 6' would have stood out in the present Arsenal midfield. The fast and free flowing game comes at the feet of a group of undersized midfield players.
All these horrific injuries have come during tackles with slower and heavier defenders. Ramsey is listed at 5'10" (the present Arsenal average) and 67 kgs while Shawcross is 6'3" and about 80 kgs. Lets apply the law of inertia. When you come at momentum and collide, it is easier for relatively larger and slower players to influence the course of motion or bring to a complete halt. In cricket, one can hit a pace bowler for a four with little force.
We are also an injury prone side - there were 5 starting players missing in the Porto game, none could be attributed to the rough conduct of opposition players. Add Walcott and RVP to the growing list of chronic absentees. There is an undoubted physical fragility to this side.
We can become part of an eternal paranoia machine or we can choose to do what Arsenal did after the injury. What should not be debated is their response.