This is very interesting question but i can't figure it out is this true or not. Near the logo of domain ask(dot)com as i can see is TM,that mean ASK word is registered as trademark.How common word like ASK can be registered as trademark?
There are actually several TM's for the word 'ask' ... its all contextual. In your eg Ask is tm'd in the context of search engines. Here is another eg of a TM application just published for objection: http://tmsearch.uspto.gov/bin/showfield?f=doc&state=4801:93tkt4.2.30