A good competitive intelligence analyst has an opportunistic side to him, being always on the lookout for possible sources of information. One example is the public computers that hotels make available, usually in their business centres. Often these share temporary or download folders across logons, so that the files downloaded, or accessed, by one person will be unwittingly available to future users. The most common 'leak' of documents in this way is when they are downloaded for printing.
However, even getting into the habit of checking the temporary folders of computers at any hotel where you stay is unlikely to yield competitive intelligence about a competitor you are actually monitoring. A more fruitful technique is to create a structured list of hotels used by competitors. When a company like Google or Boeing invites anyone to visit, they will recommend hotels from a very short list. A steady stream of visitors to the company will be staying at these hotels. On some days, it will even be clear what types of visitors these are - for example on open days for industry analysts, or recruitment days, or procurement events.
The nature of this source means any information is more likely to come from vendors, analysts, partners and other third parties, rather than from local company employees. Employees from other company offices, especially from other countries, will use the same hotels and may leave information behind - although they are more likely than external visitors to use internal company facilities for file access and printing.
And of course, all of this should be a reminder to wipe your own data after using public computers.