This have the downsides that they require perhaps pricey tools (I made use of a clicker in a single course and I feel it expense at minimum $20, so if a conference wanted to use that in an viewers of hundreds, that is a big upfront price & my working experience was that clickers were unintuitive, did not normally function, and slowed factors down if just about anything a web site would only do the job if you believe everybody has smartphones and.