State and federal court opinions are freely available from the courts themselves. Westlaw, LexisNexis, etc. gain much of their value from tools they provide for analyzing the opinions. These companies manually produce headnotes, case histories, and citation history (i.e., "shepardization"). Collating this value-added data would be vastly more difficult than automatically pulling opinions out of the PACER database (or even JSTOR). Not that I wouldn't like to see somebody try it . . .