If you can detect any type of sinusoidal variation in the velocity, then the inclination of the orbit cannot be 90 degrees with you looking at the orbit face-on. This would result in no Doppler motion towards and away from the observer. This means that you can only detect those planets whose orbits are inclined relative to the line of sight by the angle usually called 'iota', or 'i', and from Kepler's Law, the mass you get is given as Msin(i). For a random distribution of orbital inclinations, the most likely values are near 45 degrees or so, but it is common in the professional literature to estimate a maximum mass for the body in terms of 'Msin(i)'. This also means that there are probably many planetary systems that will go undetected because their orbital inclinations are too high, and the resulting Doppler shift then falls below detectability.