When I am trying to download some of the bigger apps/games, marketplace blocks the download until the phone has WiFi connection available. What is the limit for this? 10, 50, 100 MB?
The limit is 20 MB
When the download size is larger than 20 MB and you are connected on a 3g network you'll receive the "Attention required" message.
If you connect to wifi you can tap the attention required message and press retry.
Has been increased to 50 MB if you are running tango 7.5. Apps above 50 MB can be downloaded with WiFi or PC connection only.