Most efficient list to data.frame method?

Question

Just had a conversation with coworkers about this, and we thought it'd be worth seeing what people out in SO land had to say. Suppose I had a list with N elements, where each element was a vector of length X. Now suppose I wanted to transform that into a data.frame. As with most things in R, there are multiple ways of skinning the proverbial cat, such as as.dataframe, using the plyr package, comboing do.call with cbind, pre-allocating the DF and filling it in, and others.

The problem that was presented was what happens when either N or X (in our case it is X) becomes extremely large. Is there one cat skinning method that's notably superior when efficiency (particularly in terms of memory) is of the essence?