I would define "Marketing Qualified" as a person that marketing believes is ready for a sales engagement, regardless of the technical method used to make that determination.
So if you feel that leads that stop by a booth are sufficiently engaged to talk to sales, in my book that makes them MQL.
To preserve the integrity of your scoring model, you could ensure your lead scoring program adds enough points for reaching a "Visited Booth" status in your tradeshow program to ensure they hit the MQL lead scoring threshold, and then your existing threshold process will kick in.
If after considering this approach you don't feel that visiting the booth is enough to make them MQL, that might raise the question of whether those leads are actually ready to talk to sales, which could be a useful discussion to have with your sales team.
Completely agree with Justin Norris (surprise, surprise) but I'm going to add one more wrinkle to his recommendation. We had a very similar process in place, but noticed a few leads from each event wouldn't hit the MQL threshold. This was because they had negative lead scores, and the increase in lead score wasn't enough to push the leads over the threshold. This, to me, is a good argument for not allowing negative lead scores, but I lost that argument. Anyways, to ensue all leads from these and other auto-MQL sources actually became MQLs we make sure these auto-MQL sources mark the leads as MQLs.
That's a good point David. I agree with you and also generally prefer to prevent the behavior score from dipping into the negative due to inactivity, as it can create a deep hole that may prevent valid interest from allowing a lead to resurface.
But if you are going negative on the score, you need to ensure these are fast-tracked.
Christine - Ironically, I just posted our process here in this thread today: Contact - Lead Update Issue
In this specific case, these would indeed be considered MQLs (or MIOs - marketing influenced opportunities). Rather than use the lead score to trigger the sync/alerts, they would instead be fast-tracked, regardless of score.