After long time without, three review invitations in two weeks. Coincidence, or do editors share lists of helpful reviewer names? Being early in my academic career, I don't yet get many paper reviews.  Until recently, I had reviewed two papers in two years, and rejected one invitation to review.  My last review was completed some 10 months ago.

Two weeks ago, I agreed to review a paper.  Since then, I have received two more invitations.  In total, in the past two weeks, I have received as many invitations to review as in the two years prior to that.  All are from different editors, but the latest request is from a journal for which I reviewed 2 weeks ago, and comes 2 days after submitting a review to a different journal.

Although I have not calculated the probability, I guess it is unlikely that the sudden string of reviews is a coincidence.  I have the impression that accepting and quickly submitting a helpful review has caused the additional review invitations.  Which brings me to the question.

Do editors within the same journal typically share with each other names of people who have written helpful reviews in the (recent) past?  How about editors of different journals, that may or may not have the same publisher?
The journal editor (in chief) may not, but boards of editors have overlap and word does often spread that "X@Y is prompt, conscientious and fair."  

Or it could be random entropy. 

I wouldn't give it much thought. At best, you are being thought of as a good reviewer. At worst, it's a random quirk.  Choose the interpretation that makes you happiest.

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p.s. If you're feeling overwhelmed, it's entirely ok to tell a journal that you have to decline. Respond as soon as you can so that they can move on. Quick declinations (and referrals to potential other reviewers when possible) are also signs of good, conscientious colleagues. And I'm a strong believer that the good karma from these unrenumerated acts of conscientiousness will help in the long run.