For one, they should focus on areas where the reagents are not expensive, e.g. identifying novel natural biological extracts with new activities, consumer genetics (as in 23 and me), or areas such as horticulture. They should avoid things like stem cells and drug development (as opposed to discovery).
As it stands now, taq isn't ridiculously expensive, but surely open sourcing will reduce the barrier.
I make a mutation of enzyme X, then test it. Ok, the procedure works, now let's scale it to 48 mutants. Uh oh, the procedure stopped working at #28. Why? Because the batch number for our competent cells from NEB changed and it no longer accepts our plasmid. (real situation) Etc.
Imagine I want to do a PCR but can't do it myself, I must really a) have no bio facilities to speak of, b) don't know anyone else who does. What am I then going to do with the PCR product? Further, presumably I must also sent you the sample to amplify, and what kind of samples am I likely to have if have no bio facilities?
You might want to read the comments made elsewhere about something similar: http://pipeline.corante.com/archives/2014/07/09/outsourced_a...
The reagents on sale mentioned (Taq, antibiotic resistance genes and DNA ladders) are to biotech what solder and resistors are to electronics, i.e. very low value products of no use to the general public.
The real hurdle for true "biohacking" is the cost of laboratory facilities and equipment, which can easily run into a million dollars as soon as high speed centrifuges, -70 C freezers, sterile incubators and hoods, equipment for analysis, certified waste disposal facilities, etc, etc, are taken into account.
Compare this to making an app, which costs mostly the developers time and some hardware she already has lying around.