I have no personal experience and at best perhaps a vague recollection of having read or heard something, but would document images be or in the past have been used also to make discovery as inefficient as permitted for the opposition? Images require a person to analyze, or pre-processing before electronic search and analysis can be performed against them.
OCR is very good nowadays, so that's not so big a problem - and for big lawsuits (eg patent fights) there are literally hundreds of lawyers hired to comb through the vast array of documents deciding whether they're responsive or not.
The pre-processing is largely automated but there's certainly a portion (maybe 5%?) of documents that need to be hand-classified in the database before they get to the lawyers. It an interesting field - lots of money to be made, intense competition for it, relatively simple technology requirements but a legal industry which has been resistant to technology for quite a long time. Autonomy seems to be the leading software company in this space.
