Tents offer an unrivaled sense of security. But, if you can forgo that, there are some intriguing alternatives. As mentioned above, hammocks are one possibility. I thru-hiked the AT with a GoLite Cave 1 tarp and an Outdoor Research Bug Bivy-- about 28 oz after throwing out some bits. On the 3 or 4 nights that I stayed in a shelter, I could still use the Bug Bivy against mosquitos.
I think the best tents available today are single-walled designs with lots of no-see-um netting for ventilation-- essentially tarps with bug protection. Henry Shires’ “tarptent” and the Wanderlust Nomad are in this class. (I think I read that the tarptent is the most popular shelter on the PCT this year.) You could also buy a tarp and sew on netting yourself. You can get materials from Outdoor Wilderness Fabrics.
In any case, as you plunge into the sea of chatter about rainflys, vestibules, two-wall designs, etc., keep in mind that there are plenty of excellent alternative shelters that are well under 2 pounds.
Eric