I was in a hurry and ordered twelve cheap AAA batteries, rated 1000mAh, without checking for reviews and was really unhappy, when I found out after a week or so that those batteries are fake. They are branded "BTY" and came from Hong Kong. After few days of trying to 'revive' them using my PowerEx Maha MH-C9000 Charger/Analyzer, the maximum capacity reported was 190mAh which is more than five times less than the promised 1000mAh! After searching for reviews about the product, I have found a thread in the eBay discussion boards with people having similar problems like mine.

I have 36 more "BTY" batteries (AA and AAA) traveling to me and I'm not optimistic about them too. I'll try to talk to the seller, but I think this will end with some negative feedback for the seller. My goal is to stop those products from eBay or at least make consumers aware about this issue. Update: The seller fully refunded me for the first batch.

So here is my advice:

Research before you buy. If the price is low, probably there's a catch.

Check your batteries before ordering a load of them. If you don't have Battery Analyzer - read battery reviews on the internet.

If you are searching for AA/AAA rechargeable batteries - buy PowerEx Imedion (2100mAh for AA and 800mAh for AAA) or Sanyo Eneloop (2000mAh for AA and 800mAh for AAA) LSD (Low Self Discharge) batteries. A very good choice is the PowerEx 2700mAh AA size battery if you can afford charging before use (but those are keeping charge very good).

Update: hollidayp1 posted a great guide about battery testing here. It's a great addition to this one.