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No secrets with your ITU. Keep in mind, there's nothing confidential about the ITU filing. Your advantage for trademark purposes is that you have priority based on your date of filing -- in other words, you can stop later users. As you're aware, the ITU application will only ripen into a trademark registration once the mark is used in commerce. So reserving the mark is a good idea but it will have no value if you can't demonstrate your use on the goods or services.
How do you show bona fide intent? You can't simply list a group of goods and services in your ITU and expect that the USPTO will allow you to endlessly renew your ITU application. At some point, absent actual use, you will have to prove that you have a bona fide intent (BFI) to use the mark in commerce in the manner described in your application. Documentation is the key to proving your BFI. This documentation should be in the form of business plans, correspondence, product or service research, market research, manufacturing activities, promotional activities, steps to acquire distribution or licensing, expenses incurred towards your goal, and similar evidence. In addition, your BFI must exist for all the goods and services named in your application.
What's the TTAB have to say? The Trademark Trial and Appeals Board (TTAB) has held that "the absence of documentary evidence on the part of an applicant regarding such intent is sufficient to prove that the applicant lacks a bona fide intention to use the mark in commerce as required by Section 1(b)," Commodore Electronics Ltd. v. CBM Kabushiki Kaisha 26 USPQ2d 1503, 1507 (TTAB 1993). Our friends at the TTABlog have provided numerous examples of how these ITU cases play out at the TTAB. Check them out here, here, here, and here.