I've suggested that using Tridion localization works for handling certain variations for visitors, but can get difficult to manage if this is really for personalization. As an alternative to localizing templates and style sheets, I'm considering Profiling and Personalization (PnP) or SmartTarget (ST).
Can PnP or ST Component Presentation display in non-visible markup (
For PnP, having different personalization per site would require Page localization. To avoid this , could developers instead add TCDL tags manually via Page Templates (e.g.
Edit: removed suggestions and options to make the question clearer.