The queuing issue is normally at European airports that serve package holiday flights. Geneva and Chambery can be chaos at the wrong time.
Basically, the tour operators fault because they have several flights all arriving at roughly the same time, so the PAX can be distributed around the various destination resorts. For ski flights (the ones I use) there is often a Manchester, Gatwick, Birmingham, Bristol, Leeds, Newcastle, Edinburgh all scheduled to land between 9 and 10am, and each will have 150-200 holiday makers on it. So there can be well over 1000 PAX trying to get through immigration between 9am and 11am on a Saturday morning. Then absolutely nothing from noon Saturday till 9am the following Saturday.
Places like Geneva and Zurich 'should' be able to cope - these are bigger airports but they also have scheduled flights from all over the world. You don't want to land at Geneva just after an Emirates/Qatar A330 or B-777 (don't think A-380s operate into GVA thank god).
Regional airports like Chambery basically have terminals not much bigger than a portacabin with 2 or 3 immigration officials on duty for the Saturday morning rush. If it takes 30 seconds per person to do the passport checking, then handling the Saturday morning surge (1000 pax, 3 officers, 0.5 minute per pax) takes 160 minutes - basically almost 3 hours. If your flight is last to land then you're in for a long wait. Just hope it isn't raining/snowing coz the airline crew want you off the plane so they can take returning holiday makers home again, meaning you'll be stood out on the tarmac queuing to get into the terminal.
Also remember that Schengen is a stamp you in, stamp you out zone, so for every passenger arriving there is likely to be one leaving too. That means if you've got 1000 pax arriving on a Saturday between 9am and 10am, you're very likely to have 1000 pax departing home again at roughly the same time. So you're going to need another 3 immigration officers handling departures. So the airport needs 6 officers on duty from 9am to noon on a Saturday, but probably only needs a single officer to handle everything for the rest of the week.