I've done this on centuries, and on RAGBRAI. Or sometimes my paceline comes across another paceline, and the two join forces for a decent-sized fast-moving peleton.

And when riding (centuries/RAGBRAI etc.) solo, I've often picked up "passengers". These are riders whom I overtake, they like my pace, jump on my wheel, and shadow me. Why would I mind this? If I'm riding solo anyway, they do not drag me down in any way. I'll sometimes signal for them to come by and take a pull. If they can, good - we might get a paceline going. If they can't, well I was solo anyway so it makes no difference...

Back to the OP : I would not recommend it on open roads, though.