I am considering going on eBay to try and buy a new powercord for my MacBook. I know that phones often advise that you only use the official charger, so I was wondering if the same warning applied for laptops and if so, I serious I should take the warning.
Actually you should be careful when using a charger that doesn't come with your laptop. Apple's official word on the matter is:
Make sure the proper wattage adapter for your portable computer is used. Select the appropriate power adapter for your Apple portable computer. You can use a higher wattage power adapter, but you cannot use one with less wattage without potential operating issues. (here + discussion here).
In the good old days (Powerbooks) we used to get all sorts of odd logic board hassles when using the wrong charger. These days it does mean a slower charging time but it can also mean the (very) rare logic board damage or hardware funkiness.
Apple owns a patent on the magsafe connector and hasn't licensed anyone else to make one, I'd be very wary of buying a third party one if you find one at all.
However, best I can tell a magsafe charger from any macbook seems to work with any other one, but if you get one with less wattage than your original it will charge slower.
I'm not sure about Laptop cables, but I've bought at least 3 camera battery chargers over the years from eBay, each one fused in a puff of smoke when plugged in, tripping my mains fuses.
I bought my 2nd MacBook cable direct from Apple. Expensive, but the peace of mind was worth it!
Incidentally, the 'Apple 60W MagSafe Power Adapter' works fine with my old 13" Black MacBook '4,1'.