As a follow-up to my previous, let me make a concrete suggestion:
   Add this as one of the options
      df-partial-match = allowed, warn, fail

Set the default to warn for the current R-dev, and migrate it to fail at a later date of 
your choosing.

I expect that this is very little more work for the development team, it provides an 
extended grace period to those running old code that would depend on parial matching  (I 
sometimes have to recreate a 4-5 year old analysis.), it will let those who strongly agree 
migrate to "fail" immediately, and save you from the flames of those who disagree.

Some things that look good at first are not: examples from the past are na.fail as the 
default for missing values (with no global option to override) and strings as factors 
(with no option to override, global or otherwise).   There are other options that settle 
into their default and never change.  "It's tough to make predictions, especially about 
the future"-- Yogi Berra.

On 03/21/2013 06:00 AM, r-devel-request@r-project.org wrote:
> As variables in a data frame are generally considered similar to variables in, say, the global environment, it seems strange that foo$bar can give you the content of foo$bartender.
>
> In R-devel (i.e.,*not*  R-3.0.0 beta, but 3.1.0-to-be) partial matches now gives a warning.
>
> Of course, it is inevitable that lazy programmers will have been using code like

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