They could, if your website engages in the following practices for which IBM claims U.S. patent [via Tim Bray]. My very unofficial layman's interpretation follows each one.

• US 5,796,967 - Presenting Applications in an Interactive Service (Multipane dashboard with interactive user controls)
• US 5,442,771 - Storing Data in an Interactive Network (Rotating local user session data through persistent stores using GUIDs)
• US 7,072,849 - Presenting Advertising in an Interactive Service

   

  (Inline, personalized, or interactive banner ads)
• US 5,446,891 - Adjusting Hypertext Links with Weighted User Goals and Activities (Behavioral- or preferences-based personalization).
• US 5,319,542 - Ordering Items Using an Electronic Catalogue (B2B e-commerce)

IBM is taking Amazon to court today in the U.S. for infringing these very patents. The fact that Amazon has has widely promoted its HP-based infrastructure makes the case all that more chilling. I don't begrudge IBM the fruits of their R&D when they develop something truly novel, but on the basis of these ludicrous patents, we are all theoretically at risk. A possible saving grace: the USPTO has granted remarkably similar patents to a slew of other technology firms, including Oracle and 24/7 Media, to name just a few...