It would be a good thing if the hydrogen-producing algae can't survive in the wild.  Can you imagine an ocean of the algae producing hydrogen and it exploding?  Talk about climate change!

Actually, your argument is slightly flawed.  Yes, unless H2 generation by algae and the subsequent capture is highly efficient, we will be getting less energy per acre of land in use than if we were cover that same acre of land in 'high-efficiency' solar panels, but you're neglecting the costs associated.  As pointed out, to grow algae all you need is a hole in the ground full of water, and some algae to seed the colony with.  Effectively all of your cost will be in the equipment used to capture and refine the H2.  Solar panels cost money to produce, especially when we're using the relatively high efficiency ones.  Solar panels will also require maintenance, cleaning, and replacement.  Algae will just need the water topped up occasionally, plus the maintenance on the H2 collectors.  Odds are if you did the math, you'll end up with more economical energy production from the algae.  As a bonus, is you setup the algae colonies as a continuous culture, you can siphon off a steady supply of biomass for production of biodiesel, as mentioned in the article.

I hope eak will forgive me for copy, paste and edit of his comment. What to do with H2? by eak  09/29/2007 1:20 AM 

We already produce H2 = hydrogen. It is available for welding in all cities and many towns and villages. It has some disadvantages over other transportation fuels.

Suppose you had H2.  You could transport it to filling stations, compress it, and fill up vehicle fuel tanks, and then in the vehicle decompress it. This provides refrigeration which will sometimes be useful to keep your picnic cold or frozen, to cool the battery and motors and to cool the passengers. In very cold ambient, the cold is a liability. Some of the energy from decompressing can be used = see air powered car. The hydrogen feeds a fuel cell, generates electricity, then powers an electric motor.  A fuel cell vehicle (FCV) is just a battery electric vehicle (BEV) with some of the batteries (but not all) replaced by a tank and a fuel cell.  The only problem is that mobile fuel cells (e.g. PEMs) are inefficient, converting more than half of the energy in the H2 into heat instead of electricity. The heat is useful in cold weather.
What else could you do?  You could turn the H2 into electricity in a stationary fuel cell (e.g. molten carbonate, much more efficient than PEMs) and follow that with a steam turbine (sort of combined cycle).  That combination has been prototyped, and in the future with development is estimated to reach 70% efficiency.  Transmit this power over the grid (92% efficient at best), and charge a battery pack in a BEV or plug-in hybrid, and then deliver that battery power (86% or less efficient) to the motor and you get 70%*92%*86%=55% efficiency, which is higher than anything you'll get from the compress/transport hydrogen and then decompress and convert it to electricity on the road.

Of course if one had surplus electricity to start with, it would be even more efficient to just use it directly to generate H2 from electricity (50% efficient) Generating H2 from sunlight, or a SBSP = space based solar power,  might make sense, but the above analysis suggests it does only if the efficiency of sunlight to H2 is much greater than the current sunlight to electricity efficiency of 30% (cost-effective solar thermal).  Given current mobile PEM fuel cells, it might have to be as much as 60% efficient to beat 30% efficient sunlight to electricity.  That seems extremely unlikely. NREL's algae for biodiesel acheived only 7.5% efficient conversion of sunlight to oil.
Me: Internal combustion vehicles and hybred electric vehicles can use several percent hydrogen fed into the air intake of the internal combustion motor. This is almost as efficient as present mobile fuel cells and much lower initial cost.
Hydrogen can be made from electricity, economically, when the wholesale price drops to about one cent per kilowatt hour, which occurs after midnight in many locales at present and will occur afternoons in June and July in locales with lots of solar energy. This hydrogen source could total 1% of the world's energy needs, so hydrogen could fill an important nitch. Does anyone have details on the molton carbonate fuel cell? Please refute, embellish and/or comment.  Neil

Different thinking needed here... There is already a lot of talk about turning the power grid on it's head via distributed generation. It's possible to imagine a time when we have hydrogen producers scattered across the landscape including in residential areas, storing the hydrogen in fuel cells, then feeding it back up the grid to power industrial processes. This doesn't require transport in the traditional sense, just a grid that can control and aggregate multiple small power sources. The power grid, after all, should be no more of a one-way medium than is the Internet.

here in the Philippines we have a lot of abandoned prawn farms since the onset of diseases of prawn.  Might as well utilize them as the generators of algal biofuel instead of sacrificing our precious wetlands- and i agree that it would be a irreversible process if we neglect the importance of wetlands in our ecosystem.

There is limited land available for planting trees . Forests aren't the only important habitat . Farmland is an important wildlife habitat , and farmers can build up that habitat by enriching their soils with carbon , making their land more productive . The increase in productivity can be split three ways between providing more food for a growing world population , more food for wildlife and more biofuel .