Why do groundbased planet transit searches give only a few detections so far?

After the first detection of the transiting extrasolar planet HD 209458b in 1999 more than 20 groundbased transit searches has been established. the expectations to find several hundreds of transiting hot Jupiters only in a few years were high. Detections of transiting planets give important information about the orbit, size and mass distributions of hot giant planets. But with exception of OGLE-TR 56b no secured detection has been reported so far. Were these assumptions too optimistic or is there really a lack of transiting hot Jupiters? Based on our experience with the Berlin Exoplanet Search Telescope we will discuss the transit detection and false alarm rates for groundbased searches. Aspects like the number of expected solar-like stars in the observed region, binarity, geometrical probability, crowding, duty cycle, detection limits and optimized choice of the targed fields will be discussed with the aim to optimize observation strategies and instruments to reach higher transit detection rates