I say yes, but I will also support that with some of the science bit.
An unbalanced wheel vibrating as they do, can over a long period of time cause premature bearing failure. It can also wear our your tyre faster than normal. Finally in extreme cases it can also generate a highr tyre temperature which could result in a blowout.
So for the sake of a fiver, it realy isn't worth taking the risk is it?
To be quite honest, unless your wheel is damaged, the only reason you require balance weights is to offset a badly manufactured tyre. If I see more than 40 grams of lead being slapped on my wheel, I get the tyre replaced while at the fitting station. They realy kick up a stinck over it but you as the consumer have the right to refuse a product.
It might sound "picky" but I have seen first hand the damage a rear tyre blowout can do to a Lotus Elise at 100 Mph (on a test track)and I have the personal skid marks on my driver's seat too.
ATB Steve L.