A smile and a quick introduction can go along way in making these cliff side negotiations go smoothly. If you're someone new to multi-pitch climbing it's likely that the concept of being passed won't cross your mind until the day comes that somebody wants to pass you. Figuring out your systems without the added element of other climbers can be intimidating enough, and it's understandable to be uncomfortable having people climb over you. Don't fret, it's a very normal part of climbing, and given time you'll be doing the passing yourself.
This is very true, but I've had the unfortunate experience of letting parties pass and then having that immediately backfire. When I was climbing Steck-Salathe, my partner and I had these two guys climbing right on our butts for the first 8 of 16 pitches. They were from Switzerland, friendly, and seemed to be climbing pretty fast since they kept catching us at our belay stations.
My partner and I had a quick pow-wow and figured if we let them pass they'd speed right up and over the top of the climb, leaving us well behind. The Flying Buttress is a well-known and perfect mid-climb break as it's right at pitch 8 and is a giant ledge; making it easy to pass without the awkwardness of climbing over someone at a crowded belay station. We courteously asked them if they wanted to pass, they said yes and we took a nice lunch break while they climbed on. It was going to be nice to not worry about another climbing party for the rest of the climb.
Boy were we wrong.
The Swiss climbing duo came to a screeching halt and it was worse than getting stuck behind a school bus on a single lane highway. They kept calling down to us, asking if we knew which way to go...leading us to the conclusion that they didn't have a topo! They had just been following us the whole time up the route and now that we let them pass they had no clue where to go. Once the climb gets to the Narrows, it's pretty straight forward from there...but by then we were climbing in the dark...and they were close to topping out.
Needless to say we were a little miffed. They actually found us back in Camp 4 the next day (my partner and I ended up being up fro 24 hours straight completing the climb and getting back down) and gave us some beer, so there were no hard feelings held on our part.
However, let my experience be a cautionary tale to those who think about letting that party behind you pass. Make sure they're faster than you and make sure they know where they're going.