Merging SpaceX and Tesla

[sanman]

There have been a sudden spate of articles all talking about the benefits of SpaceX and Tesla merging together. No idea how credible these speculations are - there are too many to list, but here's a small selection of stories:

https://money.usnews.com/investing/stock-market-news/articles/2017-12-06/tesla-inc-tsla-stock-spacex

https://www.cnbc.com/2017/12/05/the-case-for-elon-musk-to-combine-tesla-with-spacex.html

https://www.bloomberg.com/news/articles/2017-12-05/spacex-seen-as-potential-suitor-if-tesla-struggles-musk-wanders

http://www.businessinsider.com/tesla-and-spacex-merger-makes-sense-morgan-stanley-2017-12

http://dailycaller.com/2017/12/06/elon-musk-could-combine-tesla-and-spacex-setting-up-another-huge-conflict/


How well grounded are these speculations - or are they just an attempt to pump Tesla's stock?

What sort of forces would be driving such a merger?

Would such a merger really be in the interest of both companies, given the existing missions of each company?
In what ways would each company benefit?

What are the downside risks?

[RotoSequence]

Elon is keeping SpaceX under his control until regular flights to Mars are underway. Obligations to shareholders are an obstacle to developing their Mars architecture.

[gongora]

An analyst at Morgan Stanley wrote in a report that he thought it would be nice for them to merge.  A bunch of people wrote about the report that came out.  That's all there is to it.