12. A system for crawling network-accessible documents, comprising: a network interface; a crawler programmed to request the network-accessible documents from one or more websites over the network interface and to obtain information from the network-accessible documents using a first agent defined to obtain information from documents having HTML-formatted information and a second agent defined to obtain information from documents having a mobile content format; and a format selector operative to switch the crawler between obtaining the information using the first agent and obtaining the information using the second agent.
12. A system for crawling network-accessible documents, comprising: a network interface; a crawler programmed to request the network-accessible documents from one or more websites over the network interface and to obtain information from the network-accessible documents using a first agent defined to obtain information from documents having HTML-formatted information and a second agent defined to obtain information from documents having a mobile content format; and a format selector operative to switch the crawler between obtaining the information using the first agent and obtaining the information using the second agent. 17. The system of claim 12 , wherein the format selector is further operative to switch the crawler to impersonate a number of different agents in obtaining information from documents.