While lists like these are always somewhat subjective, I think I'd have to agree with most of PC World's new List of the Worst Tech Products of All Time. Especially their No. 1 pick -- AOL!
Way down the list near the bottom is one of my personal favorites: The CueCat. This was a stupid white widget that you plugged into your PC to scan special codes into your computer from magazine ads (!). So if you were looking at a travel magazine and they had a special CueCat barcode at the bottom of the page, you'd scan it and immediately get diverted to the right web page for more information. Interesting thought; but that meant you had to have the magazine in your lap with the page open to the ad, a CueCat in your hand AND an Internet connection. But wouldn't it have been easier for someone to simply TYPE the web page into their browser? Anyway, after raising millions (and I mean MILLIONS) from the likes of Radio Shack and Forbes Magazine along with numerous VC's, the company crashed. But not before their entire user database got exposed to hackers (I still remember that fiasco).
CueCat was probably among the list of the worst VC investments of all time as well (IMHO). Accordingto WIRED, it's clawing its way to a comeback.