Hi There
I hope you don't mind an honest answer ... it kind of pains me as a domainer to say this but ...
Let's take virtualtrainers.co.uk. The virtual training industry is likely to grow further worldwide, it's probably in the billion pound yearly spend region already and growing.
However, when it comes to the domain, there's sadly relatively little value in it. This is because it is non-distinctive and can't brand a company in the marketplace. This means the domain is of no value to the multi-million pound companies that operate in the space.
So, the only thing the domain can be used for is to put up an information site. However, the domain itself offers no major business advantage.
I hope that helps.