Valve wouldn't be impressed by this as I assume that part of the deal for companies like Jolt providing the content servers is that their ads get seen by the 2.4million users they have.
Blocking adverts, unless they're incredibly intrusive like pop ups/unders, gigantic Flash adverts, ones that make noise or generally ones that are an incredible nuisance is a bit unfair.
You're able to use the Steam service because of those adverts, without them it wouldn't be as efficient.