According to the official game's site 2K decided to remove SecuROM install limit after community provided massive feedback on the subject.
There will be no SecuROM install limits for either the retail or digital editions of BioShock 2, and SecuROM will be used only to verify the game?s executable and check the date. Beyond that, we are only using standard Games for Windows Live non-SSA guidelines, which, per Microsoft, comes with 15 activations (after that, you can reset them with a call to Microsoft.)
What does that mean for your gameplay experience? This means that BioShock 2?s new DRM is now similar to many popular games you advised had better DRM through both digital and retail channels. Many of you have used Batman: Arkham Asylum as an example to me, which uses the exact same Games for Windows Live guidelines as us as well as SecuROM on retail discs, and now our SecuROM is less restrictive on Steam.