Mainstream scientific thought endorses algae-based biofuels but with realistic expectations. People who've done the math know that replacing a small portion of America's liquid fuel would require devoting enormous amounts of farmland to algae crops with very low yields. This does not mean algae-based biofuel should never be produced under any circumstances. It means there is a niche somewhere for limited production that doesn't crowd out food crops. Seaweed-based biofuel may avoid a food vs. energy tradeoff.
People who haven't done research take the easy way out and seek government subsidies. The algae-fuel industry is pushing for federal tax incentives that will put it on the same footing as the ethanol industry. That is very premature and probably a poor use of public money. Ethanol is a controversial energy source because it does not always produce a positive EROEI. Factoring in energy used in fertiliser added to crops gives ethanol a negative EROEI. Growing it organically gives it a positive EROEI but, like all things organic, limits the yield. Algae-based fuel must not fall into the same trap if it is to be viable.
Full disclosure: No investments in biofuel companies at this time.