Sorry guys. A hydrogen economy won't save the earth. In fact it will possibly do the opposite.
Your choice as first post as a wannabe-spambot is as hilarious as it is erroneous. First, you necro a thread that's seven and a half years old, that's the hilarious bit. Then you offer up a real gem of ignorance and paranoia: splitting water will cause water to run out, and we'll all parchify to death OOOHH NOOOEEESSSSS!!!
You better tell the trees and every other photosynthesizing organism on this planet that they must stop what they're doing IMMEDIATELY, because our precious hydrogen will escape our atmosphere and we'll all DIIIIIIEEEEEE!
"But... We've been doing this for literally billions of years!", the plants and plancton respond.
"Oh", you then said. "Well... Okay then. Carry on."
(Btw, this is what photosynthesis is, btw. Splitting water and combining hydrogen with carbon dioxide to form sugar, which the plant can then use to make starch, cellulose, fats and so on.)
Anyway, you might want to read this as an analogy for your fears:
http://what-if.xkcd.com/53/
It describes a scenario where a ten-meter diameter hole to outer space is placed at the deepest point of our oceans, and then asks how long it would take for said oceans to drain. Relevant quote:
Randall Munroe said:
What happens to the Earth?
Not much. It would actually take hundreds of thousands of years for the ocean to drain.
SO, since we actually re-combine the hydrogen with oxygen when we want to generate power (thus re-creating water), there's no point in fearing that we'd run out of either hydrogen or water anytime soon. Also, from what I've read, free hydrogen in the atmosphere is quite reactive and tends to spontaneously form water, so it's unlikely that any waste hydrogen seeping out of leaky valves or whatever would be able to make it to the top of the atmosphere and escape. It takes a while for gases to make it way up to the top.
Anyway, it might interest - or frighten - you to know that we lose atmosphere to outer space ALL THE TIME, ERMAGHERD!!! We're all gonna suffocate!!!!11!1!1!!222 Apparently, our own sun sends out high-energy particles that are mostly deflected by the Earth's magnetic field, but around the poles there are holes so to speak where impacts can knock air molecules into space. Cool, huh?
And yeah, it would take a ridiculously long amount of time for all atmosphere to bleed off this way as well.