Anyway, the standard peakist response is:
We have no way of knowing whether they actually have the spare capacity they claim. Since it's in their best interest to claim spare capacity, the claims are automatically suspect unless they are reflected in the a rise in actual production figures. That has not been much in evidence recently.
Peak production is on of the things that can affect price, but not the only one. High prices are not necessarily evidence of Peak Oil, in the same sense that weather isn't evidence of climate change. However, to draw out the analogy a little more, price instability within a long-term rising price band (especially in the absence of major changes to the marketed volumes) can be taken as one good piece of evidence.
Most floating storage is used in conjunction with offshore production, as sort of an oil staging area. A list of these floating storage units and the fields they are assigned to can be found
here.
Tanker storage is a bit of a red herring, because it's an ongoing phenomenon that is used to greater or lesser extents depending on the amount of contango in the oil futures market. The volumes they store are insufficient to affect global supply over any extended period. The most I've seen reference to being stored at any one time is around 120 million barrels in 2009, maybe a day and a half's consumption. I've seen references to the current floating storage being about 30 million barrels. In a sense the floating storage is used by producers to stabilize the market - they put oil in storage when prices are low, reducing supply a bit and moving prices up (as they did in 2009), then taking it out of storage as prices rise, thereby increasing supply and moving the price down a bit. It's really more of a buffer than a gouge. Here is a more extended discussion of the issue:
http://www.oil-price.net/en/articles/the-case-for-floating-oil-storage.php">The case for floating oil storage.
Feel free not to believe any of this if it doesn't suit your world-view.