This has always bugged me. Still in Beta-2A so I thought I'd make a post.
When you capture a planet, you always steal an enemy tech. The problem is that you can steal any tech from them. I am using Laser Vs and I just stole Singularity II from the enemy. I have never researched anything in the mass driver line. That is problem #1. Problem #2 is that I can now research Singularity III, skipping all of the previous mass driver techs. Third problem (more of an exploit) is that you can leave a newly conquered planet undefended and then get another free tech.
I know everyone loves getting free tech from a successful invasion, but please let's keep it in the same sector with game balance. You have a chance (like 25%) to steal a tech and you can't steal a tech you don't have the pre-reqs for.