I would like to bump this to see what side of the fence fonz is finally going to fall on. All of you newbies who flamed me especially need need to read this. Here is a copy of a post from AF (by far the board with the most intelegent people) made by Coroner. Most of you will know his reputation and qualifications.
Short answer: YES filtering is sufficient.
Long answer:
99.9% of all bacteria are larger than one micron; most are on the order of 1-10 micron. That's pretty big, if you think about it- although it still may be undetectable by the human eye. Most people agree that anything below about 30 microns is not detectable without a microscope or something better than our eyes.
There are, however, bacteria that can be smaller than 1 micron. These "new" (new in the sense that we are only now learning more about them) bacteria are called mycoplasma- so called because they lack a cell wall- can be between .1 and 1 micron. These are the "bacteria" that supposedly cause Gulf War Syndrome, CFS, and a bunch of others. However the lifespan of these guys outside of the body is less than a couple hours; they need a host to survive. I really don't think that we need to worry about them, especially if you're careful while brewing your stuff.
The other answer is that filtration is the method of choice to sterilize drugs manufactured by the drug companies (assuming that the drug itself is small enough). The reason is that most drugs, our hormones that we like to inject included, can be heat-sensitive and there is no sense in heating the stuff up if you can just filter out all of the heebie-jeebies.
Here is a link to the post on AF:
http://anabolicfitness.infopop.net/2/OpenTopic?a=tpc&s=702093973&f=312093973&m=8973013286
If you need more convincing do a search on AF and you will be reassured.