Get Free Access to Pay-Walled Content with a Simple Google Hack

They could always make only a portion of their article available - say, the first paragraph or two. Some sites do this for non-paying users. Admittedly, the content-free nature of such a choice might adversely effect their standing.

Or implement a server-side thing to check if the requester is a googlebot, and if so give them the entire page, or if not ask them to register/pay. Might raise some issues with Google's cache, but that could probably be worked around (does Google allow sites to opt-out of that? Does that influence their positioning?)

EDIT: Having noticed that Google refers to this as cloaking, and dislikes it rather extremely, I'm having a bit of trouble figuring out what would work better. So, it does seem like a bit of an issue ...