Random force closes are only suspicious if it's truly random (i.e. no plausible causes) and it's only happening on your device. In most other cases, it's simply due to poorly coded third party apps.
There are two kinds of force close dialogs:
- Android offers to force close applications that fail to respond to an input event within five seconds. When this happens, the force close dialog offers you to either "wait", "report", or "force close" the app (this is also called the ANR/Application Not Responding dialog).
- There is also another force close dialog that happens due to an unrecoverable crash or unhandled exception (e.g. null pointer error, stack overflow, array out of bound, etc). This crash dialog would not offer you to "wait", just to "report" or "force close".
In any case, check the report dialog and see if you can scrap any useful info (most importantly, the traceback) to determine whether it's an application bug. Google the traceback message with the name of the app to see if it's probably a common issue with that particular version of the app.
Make sure you keep your apps up to date.