imo.imは安全ですか？

You if read the terms of service, you will understand that you basically cannot trust this service because on accepting their terms you grant them full access to use any information you send through imo the way they feel. From terms of service (https://imo.im/terms) [...] In these Terms of Service, “Content” means text, images, graphics, audio, video, software, location data, usernames, and all other forms of data or communication. “Your Content” means Content that you submit or transmit to, through, or in connection with the Services. [...] 10. Content Our Rights to Use Your Content We may use Your Content in a variety of different ways as permitted by our Privacy Policy, including, without limitation: PUBLICLY DISPLAYING IT; reformatting it; incorporating it into reports, collections, marketing materials and other works; creating derivative works, summaries, or aggregations from it; promoting it; distributing it; and allowing others to do some or all of the foregoing. As such, you hereby grant us world-wide, non-exclusive, perpetual, irrevocable, royalty-free, fully sublicensable (through multiple tiers), transferable rights to use Your Content for any purpose permitted by our Privacy Policy (including, without limitation, the rights to use, reproduce, publicly perform or display, distribute, adapt, publish, modify, translate, incorporate into other works in any form, media, or technology, and create derivative works of Your Content, in whole or in part, throughout the world in any media).

imo.im is a great way to communicate with people when you're not at your own computer. They keep all your messaging accounts in one place, and chat is over HTTPS, so you (usually) don't need to worry about security. I've been using the site for over a year now, and their service and reliability has been growing by leaps and bounds.