Or worded differently:

Has anyone heard of "big" SEO companies removing links after termination of service?

I have a client who isn't particularly happy with the SEO he's getting from a big Aussie SEO firm, and he wants to terminate, however they've built thousands of links for him and he's a little concerned they might all get pulled.

Has anyone heard of this happening, or;

Do you think this is a legitimate concern?

I think its physically possible to remove backlinks like this because it seems the SEO firm in question is building links by using other client's websites.

I also wonder if they might have large content farm style sites where they place links for clients which might be quite easy to take down.

Please discuss!