Consider the four-color theorem. The original proof requires the use of a computer to check billions of cases; here's a link to another proof, where the author says
"The first proof needs a computer. The second can be checked by hand in a few months, or, using a computer, it can be verified in about 20 minutes."
As a general rule, given any formal system, and given any positive N, there will be theorems in it whose proof requires at least N steps. That's any N - eg 10 to the 10 to the 10 ... to the 10.
I maintain that computer programs are implementations of human reasoning, thus all of their results fall under that heading.
In other words, there are proofs that require an infinite number of steps? That's the immediate implication.
I guess it'd help me if I understood whether we are talking about proofs in general or only about algorithmic "proofs." It's true that there are brute force proofs which take a huge number of steps to check every case, but of course that doesn't imply that more "elegant" solutions don't exist. The four-color theorem may be a case in point.