Using that many plugins is an absolute nightmare in terms of performance. A year ago it wasn't a big deal, but with Google now factoring load time into search rankings, you gotta cut down on that. And most useful wp plugins can be duplicated in a theme pretty easily.

Also, I fail to see how one would be locked into using a certain theme if you build in plugin functionality. Couldn't you just install the plugins in the event that you wanted to switch themes? Seems far more efficient from my perspective. I guess from a basic user point of view plugins are great, but IMO any wp theme worth its salt is going to have a large amount of commonly used plugin functionality built in.