[JeBuS]

Well, there's still the limiter that you can only seed 2 of each. So yeah, it could get fun on the spaceline if both players are seeding 2 of all of them then just attempting and getting them all out at once, but it's not exactly spam as it's generally known.

[Enabran]

Don't forget Obsession and Urgent Warning

[JeBuS]

Don't forget Obsession and Urgent Warning

Again though, that doesn't really reach the level of "spam". Obsession is once per game, at the start. Urgent Warning is (basically) once per turn in general, and further limited to once per game per card title. I don't think a maximum of 4 copies of a single and 3 of any others rises to the level of spam, especially when 2 out of those 3/4 need to be encountered under a mission.

[winterflames]

Yeah, but all those dilemmas, Whale Probe and the Nexus, plus some Cytherians and Emergent Lifeform action and a theme deck and you can set up a pretty busy space line!

You probably won't win, but you can trash the spaceline and use UFP to fly from one time location to another and avoid it entirely.