Increasingly, businesses are looking at controlling the wireless space within their facilities. In some cases, the intention is to ensure maximum coverage and throughput for all users, and to minimize interference. In other cases, facilities are looking to maximize revenue for in-building wireless systems installed by the facility owner. And sometimes, theatre owners are just looking to keep cell phones from interrupting shows.
Caution must be exercised, however. Signal jammers are specifically prohibited by the Federal Communications Commission. Those violating the Commission's rules can be subject to very significant fines. For example, Marriott International will be paying $600,000 to resolve an FCC investigation into whether Marriott intentionally blocked WiFi signals at its Gaylord Opryland Hotel and Convention Center, in order to force customers to utilize Marriott's WiFi network at up to $1,000 per device. The FCC's Public Notice on the case can be found here: http://www.fcc.gov/document/marriott-pay-600k-resolve-wifi-blocking-investigation.