Installing toolbars is basically like sharing a virus and getting paid. You are selling yourself out cheap. Many toolbar "products" do such nice things as strip referal codes, redirect surfers, and generally take all your hard earned traffic away from you.
Put it this way: Say you are promoting "DirtyGirlDollars" sites. After you have gotten a surfer to install a toolbar, any time someone clicks on a link to a DGD site, suddenly the sponsor code is switched on the way to the site and the toolbar people get the sale.
You just trades $30 for $0.15.
The more toolbars installed out there, the more free site traffic becomes worthless, because the toolbars get between your surfer and your sponsor, literally sucking away your income.
If you promote toolbars, your the tool.
Alex