I will also venture the perhaps controversial opinion that you're not prohibited from looking at webcams or getting your mate to look out the window when thinking about your upcoming flight, you're just not allowed to make operational decisions based on non-approved sources.
However, as long as you do have all the appropriate forecasts that say you can go (with alternate if needed) then other unofficial sources are a bonus.
Also, a look at a webcam is a (non-approved) observation, and as we know obs and forecasts are very different things. I bet, though, if the bom had access to handy webcams in clag-prone areas they'd use them to help with the forecasting, so maybe it could be a goer. That would also bypass the 'approved observer / source' problem.
Otherwise, they'd be no different to the rain radar pictures they put up now, bloody handy but not to be used in lieu of 'proper' forecasts.