For those who don't want to read the whole question:
Battery drains extremely fast when surfing the web, but not fast at all when watching videos.

Ok, so...

When trying to surf the web for more than a few minutes at a time (over WiFi or 3G) the battery usually drains crazy fast. It does this no matter what browser I use (stock, Opera, Boat Mini, Next Browser, etc).

The battery will go from 100% and drop to 50% in about 10 minutes of straight web browsing, then it will drop to 30% or 20% in a matter of a minute or three. Then I'll get a low battery warning and the phone will shut off.

Here's the kicker. I tried testing the life of battery the other day by going to you tube (via the app) and playing a full length concert, purposely leaving my phone unplugged. The concert played (over WiFi) for 1hr and 40m before the phone shut down!!

There's no rogue app draining the battery at this time. The ebay app was draining it in the past, but I uninstalled it.

And here the thing. Even after the battery goes dead and the phone shuts off, sometimes (not all the time) when I plug it back into the charger it will say it's 50% charged right away and will be 100% charged in a matter of 10-15 minutes! other times it will take two hours. What's going on? Bad battery? or just the way it is?