According to McAfee there are 225 Malware ToolBars.
Full List Here:  McAfee Link

And A search on Symantec comes up with 100 of them.
Full List Here:  Symantec Link

Now here is something else to think about... there is a toolbar called  "AskJeeves Toolbar" to use the AskJeeves search engine.  The Toolbar is legit, however its is prone to a buffer-overflow vulnerability one of the most common vulnerabilities in software.

So Although the ToolBar is Legit, a Flaw in programming, could allow a potentially malicious website to use this flaw to cause harm through the tool Bar.

I've found myself accidentally visit a site that I thought what the information I was looking for, but turns out to be a malicious site.  My Spyware software caught it in time.