I saw this press release from Thompson ELT and TESOL talking about the success of some webinars they put on. Almost zero news value. No way a journalist is going to pick up the story and write more about it. And an excellent job by the companies involved.
Press releases of this type should be part of an overall marketing strategy associated with your webinar planning. It leverages the fact of the webinar to get additional awareness of your company and its beneficial offerings. It projects value in the outreach and services you are providing to your customers or to the community. It gives you additional inbound links to your company website.
Notice that because their webinars incorporated a simple post-event survey or poll, they were able to put hard numbers and statistics to their attendee satisfaction and show that their events are worth the investment of time (and possibly money... I couldn't tell if they charged).
The only thing I would have pushed for if I had been writing this release is a slightly stronger call to action at the end. The release says that they are planning additional events in October and November. They give a link to the generic home page for the company. It would have been nice to give people a link to the specific page that lists past and future events. Maybe an access point for listening to recordings of the archived events (that can be an additional revenue generator if they are fee-based seminars). And I would rephrase the final sentence in the active voice to tell people to visit the site, rather than a passive line saying that information can be found there.
But that's nitpicking. Remember that the usefulness of your event does not end when the event is over. You can continue to benefit from it in marketing and communications. Take a lesson from Thompson and TESOL.