Many websites have Terms of Service that say something to the effect of "We reserve the right to amend this Agreement at any time and without notice." I would argue this kind of language is dangerous and may cause your Terms of Service to be entirely invalid. Why? Because a Terms of Service agreement is basically a contract, and a contract where one party can arbitrarily change the terms of the contract may be considered illusory.
In the Harris v. Blockbuster case earlier this year, the Terms of Service were found to illusory because Blockbuster could arbitrarily change the terms and they would take effect upon posting. To quote from the decision:
The Court concludes that the Blockbuster arbitration provision is illusory for the same reasons as that in Morrison. Here, as in Morrison, there is nothing in the Terms and Conditions that prevents Blockbuster from unilaterally changing any part of the contract other than providing that such changes will not take effect until posted on the website. There are likewise no “Halliburton type savings clauses,” as there is “nothing to suggest that once published the amendment would be inapplicable to disputes arising, or arising out of events occurring, before such publication.” The Fifth Circuit in Morrison noted the lack of an “express exemption” of the ability to unilaterally modify all rules, which the Blockbuster agreement also does not contain. The Blockbuster contract only states that modifications “will be effective immediately upon posting,” and the natural reading of that clause does not limit application of the modifications to earlier disputes.
There seems to be no fail-proof way to avoid this. As a reasonable best practice, consider using an approach similar the following:
- Give a reasonable time period after you post the change to the Terms of Service before they take effect (such as one week).
- Keep a history of changes at the bottom of the Terms of Service which summarizes the change (it's unreasonable if the user needs to reread the entire Terms of Service to spot the change).
- In addition to posting it on the website, email users (if you have their email address) and provide an RSS feed so users can opt-in to see changes (without having to provide their email address).
Hat tip to Eric Goldman