If budget is unlimited.. then need to consider all those comments mentioned..
If got budget constraint, the 18-55IS + 55-250IS cost less than 18-200IS and have a reach of 18-250mm.
With that reach, as a beginner venturing into photography, it's possible to explore the different genres.
If a beginner is concerned about having to switch lens, whether lazy or afraid of missing that moment.. then I have no further comments.
I feel that beginners should be more concerned about the basics of photography to get the exposure correct then worry about "missing the moment" due to lens change. That would be post-beginner stage. By then, probably the user would be more clear on what he/she wanna shot and choose the next lens carefully.