I would not place the chances of such a body existing at more than 5%. Despite this I would say that it would not hurt to look, were it not for the facts that

1) rigorous modeling has shown that the gravitational effects of our solar system passing though the plane of our galaxy are sufficient to account for the injection of cometary impactors.

2) The Nemesis hypothesis seems to require a MAJOR impact rate of around 1 per 100 million years, rather then 1 per 26 million years, which is what the data appears to show.

3) The Nemesis model thus understates the major impact risk by something like 4 times.

4) The Nemesis model thus also obscures periods of high danger.

5) The Nemesis model places the cometary impact risk at an impossibly low number: 1%, where the Saturn data appears to indicate that it is more than this.

6) 20 years of money spent on tying to find Nemesis has resulted in exactly no result, in other words, most of the the money spent after the first searches appears to have simply been wasted.

Since money is limited, I think it would be more useful to spend this money on crater counts on the new Saturn imagery and on the development of accretion models which actually account for the observed data. SWRI could easily better use this money now, as could many other groups.