Even though this is an old thread revisited, just in case someone who reads it missed the new TSA battery regs, please be aware that it's highly unlikely any DSLR batteries you take in carry-on luggage will exceed the minimum 8 grams limitation where the two battery limit takes effect. See the following article regarding this:
Rules clarified on flying with lithium batteries - USATODAY.com
Note that they state:
"One exception: Passengers toting lithium batteries that have 8 to 25 grams of equivalent lithium content are limited to two uninstalled batteries in each carry-on. Most consumer electronic goods such as laptops, digital cameras and cellphones use batteries that fall far short of that content."
They also say:
"However, unlimited loose batteries
are allowed in carry-on bags, though the agency "strongly recommends" separating them in individual zippered bags or compartments if they aren't in their original packaging."
What you CAN NOT do is carry spare Li-ion batteries in your "CHECKED" luggage! But you CAN carry unlimited ones that meet the above standards in your "CARRY-ON" luggage.
This is in agreement with a variety of other articles and posts I read during the initial flurry of interest in this. One post that I can't find even calculated the amount of Lithium in pro DSLR batteries, showing how little it was compared to the TSA standard. Where this comes into effect is with film crews, etc., with high capacity video and other equipment batteries that are huge by comparison to DSLR batteries.
Here's one more thread that says it quite well:
GottaBeMobile - New Battery Rules For Air Travel Effective January 1 : Tablet PC & Mobile PC News & Video Reviews, and Tablet PC Forums
If almost all laptop computer batteries fall under the 8 grams limit, the DSLR batteries must also!