legal for registrars to speculate and reserve domain names?

I had an odd thing happen yesterday... I queryied the networksolutions.com WHOIS database to check on availability of a specific domain for a client; it was availabe.

Today the client asked me to go ahead and register the domain, but lo and behold, networksolutions.com has registered it, and there is no associated website. Is this coincidence? Did they use my query to automatically 'taste' the domain on the odds that i would be trying to register it and force me to BUY it from them?

In a more general sense... what IS the policy for resolving situations where registrars, or individuals reserve 'likely' domain names with no intention of creating websites? It might be difficult to police this with indivuals since they could put up a simple one-pager saying that the name was for sale. BUT for a registrar to use a WHOIS query to register a domain before you can get to it seems highly unethical.

CAN we control this practice? CAN we make registrars 'release' tasted domains that they do not intend to actually use?