Situation: Your opponent notices a deposition. For one reason or another, you want to videotape it. Do you need your opponent's consent?
Obviously, the answer depends on the jurisdiction. The issue recently led to a dispute in New Jersey, as recounted here at Law.com. In short, the defense lawyer noticed the plaintiff's deposition and the plaintiff's lawyer wanted to videotape it. Since the plaintiff had suffered a brain injury, the plaintiff's lawyer wanted a record of the plaintiff's difficulty in answering questions. This difficulty might not be evident from the dry printed transcript, which wouldn't record pauses and the like.
As the rules in New Jersey didn't expressly provide for one party to videotape another party's deposition, the dispute had to be resolved by the court, which allowed the videotape. The decision is posted here (pdf).
What's the rule in Illinois? The situation is easier, as the rules expressly provide for videotaping another party's deposition. According to Rule 206(a)(2)--
(2) Audio-Visual Recording to be Used. If a party serving notice of deposition intends to record the deponent's testimony by use of an audio-visual recording device, the notice of deposition must so advise all parties to the deposition. If any other party intends to record the testimony of the witness by use of an audio-visual recording device, notice of that intent must likewise be served upon all other parties a reasonable time in advance. Such notices shall contain the name of the recording-device operator. After notice is given that a deposition will be recorded by an audio-visual recording device, any party may make a motion for relief in the form of a protective order under Rule 201. If a hearing is not held prior to the taking of the deposition, the recording shall be made subject to the court's ruling at a later time.
Illinois Supreme Court Rule 206(a)(2) (emphasis added). Though the rule allows videotaping without the need for consent, it also provides any party with the right to challenge the videotaping by way of a motion for protective order prior to the deposition.