So the FAQ says that unless the runner is prevented from jacking out, he is responsible for indicating a number which immediately resolves and then jack out if the run was still not successful at that point.

So if I'm playing against a runner with 2 link, does that mean I can put a TMI in front of a server, and just keep rezzing it infinitely until the runner must jack out?

Edit: Nevermind guys, I found the answer.

Well, assuming you can keep paying for TMI due to a reduced rez cost (such as Akitaro Watanabe and/or an overscored Brainstrust) then yes, onus is on the Runner.

I assume you found the answer in the FAQ on infinite loops?

Actually, according to a quick google search (really should have done that before making the thread), It was ruled that the onus is on the Corp to end the loop.

I'm assuming this differs from Cell Portal because the corp has the chance to beat the trace but opts not to, thereby giving the runner no chance to react to anything.

Ah yeah I see what you mean. The runner actually has no opportunity to jack out during the rez window so the onus is on the corp here.