What's fascinating to me is that this layout makes it much more difficult to understand the timeline as linear since you have to read across the page (left-to-right) and down with noted differences in the sizes of each tweet.

It's the effect of reading all tweets at once instead of focusing in a single tweet at a time. Clutter adds distractions which take away from the value of each individual tweet.

However, when I hit a batch of tweets that are primarily photos (as opposed to pure text and links), it's much easier to understand what's happening.