I like the qualifier “do you use this service provider yourself?” and point about context mattering. If a service provider has been used for a long time, that’s probably a good sign. There’s one caveat, though. Some referrers get into a rut and continue using the same provider out of laziness or habit. But they don’t want to admit they’ve made a suboptimal choice. So they may give a favourable recommendation where one isn’t warranted. Buyer beware.