One of the most frustrating things about webmeetings or virtual team gatherings is that you don't hear from everyone. In fact, you tend to hear from a chosen (frequently self-selected) few. So how important is it that you hear from everyone? The secret is to separate input from speaking and understand that there's a distinction between getting input and the form that input takes.
Think of it this way: input is your best thinking, ideas, feedback and comments. Speaking is just one way of transmitting that input - verbally, whether in person, or on a phone or webmeeting. But that's only one way of getting your thoughts clearly and effectively to others.
Speaking for yourself serves a critical function in long-term team building and ongoing work relationships. Through the way we speak, people form impressions of our style, our intelligence and the quality of our work. When those impressions are positive, that's a good thing. We know the reverse is also true.
Frequently the fear of how we'll be perceived holds us back from speaking. Remember that a goodly percentage of the population suffers from fear of public speaking (which has lots of similarities to speaking through the phone or media). Add thick accents, shyness (not to mention the fear of getting caught answering email instead of paying attention) and there is no shortage of reasons people don't just pipe up.
So what are some of the alternatives to just asking people to "just chime in when you're ready"?
Consider chat an asset instead of a distraction. Many people, especially the extremely introverted or those with thick accents, aren't comfortable speaking in a virtual environment. They are much more comfortable writing their thoughts down before contributing to the group. Is that such a bad thing? Additionally, you can keep the chat log for later reference which can also add value.
Use sub-groups to get input from everyone, but not everyone has to contribute in the main meeting. This allows everyone to be heard from, but they don't have to necessarily speak for themselves. You can use virtual breakout rooms and subconferences (if your platform offers that feature) or simply assign work to small groups and reconvene when you're ready.
Have non-threatening, structured methods for generating feedback. A good white board discussion is easy to hold online. If everyone knows they are expected to participate it won't be so traumatic when people are called upon. This means that you should give them some warning their input will be expected (put it in the agenda so people can't claim they weren't prepared) and you can call on the reluctant people later in the session so they can gather their thoughts.
Use asynchronous methods. One of the most under rated luxuries in the workplace is time to think. Does the situation require everyone's input right this minute? Does the decision really need to be made on this call? If not, why not start the discussion, then encourage people to use discussion boards, wikis and tools like Sharepoint or internal Facebook-style pages to allow them to contribute when they've actually had time to think about it and formulate their ideas clearly. The best ideas aren't always the first ones to be offered up. In fact, they're usually not.
Remember that sometimes there are perfectly valid reasons for not speaking up on calls. How many of us have had to take a conference call while waiting for a plane, or in the car between sales calls? Starbucks is fine for coffee, not so much for nuanced discussions of engineering or strategy.
Of course, the best way to ensure input from everyone on a team call is to create a culture where people know their input is expected, valued, and the terminally extroverted or opinionated won't be allowed to dominate.
That's down to us as leaders.