It is a very real possibility and the community will be warned.
You are currently trusting all of your dollars (assuming US) to just a few people meeting behind closed doors, who are currently using extraordinary measures to prop up a struggling financial system. Their interests are not always aligned with your interests.
The pools do not own the hashing power. At the slightest hint of impropriety, the hashing power will be yanked.
We have two pools, who
do not own anywhere near 51% of the actual hashing power, and who would have to collude to together to destroy their own businesses, just doesn't seem like much of a risk. Their interests are aligned with ours.
My life can be ended instantly by any of thousands of vehicles every day if they choose to cross two painted parallel yellow lines. Because it isn't in their interest to cross those two lines, I trust my life every day that they'll stay on their side of the road.
A few facts:
1. If a pool, or even an individual has 100% of the hashing power, you do not lose your bitcoin unless they choose to 'cross the yellow lines' and act suicidally against their self interest.
2. You do not lose your bitcoins even if they do act against their self interest. Your bitcoins will be safe - except possibly a few that you receive during the timeframe of a malicious attack which will be very short lived. There are just too many people watching the blockchain.
3. If attack of this sort happens, which is possible, but very, very unlikely, the miners will pull their hashing power from the pool, and the attack ends. And, very likely the pool ends as well.
I'm all for distributing the hashing power, but the problem is being overstated.