That is the question.
Whether 'tis nobler to suffer the slings and arrows of outrageous fortune
at only one table,
or to take up mouse against a sea of fishy Party Poker tables,
and by opposing,
end up richer.
Apologies to people who actually may revere Shakespeare like all my boring-arsed English Lit professors did. Jebus, people, he wrote dick and fart jokes! Well-crafted dick and fart jokes, but the original Slick Willy's shite was at least as raunchy as Daddy most days.
Anyway, back on topic.
It's always a question for me how many tables to play, and why. When I first started playing online, one table was more than enough, even at the lowest of limits. I could barely keep up with reading the board and my hand, then thinking about outs and draws, much less trying to put an opponent on a hand, so playing more than one table was out of the question. Not to mention the 15" CRT I was playing on wouldn't support more than one screen with any reliability. Now I played mostly limit, and as low as I could find, so it was all pretty straightforward.
As I have begun to get the hang of playing (I can almost always tell what my hand is now, and occasionally can hazard a guess what some other idiot is packing), one table becomes far less interesting. There is still data mining to do, watching for betting patterns, etc., but this is less useful in large-field MTTs, as your tables shift so quickly and you may never find these same lemurs again, so paying close attention to these folks is not as valuable as it is in some other cases. So I began to venture into playing more tables at once. It's taken some experimentation to figure out the best method for me, and I'm sure as I log more thousands of hands my number of comfortable tables will increase, but here's where we are today.
I'll play two tables of no-limit or pot-limit comfortably, and up to 4 tables of limit. But I don't play much limit, so it's kinda moot. I try to stick to the same game on most tables, but I may throw in a low-limit stud Hi/Lo on top of two tables of NLHE just for the sake of mixing things up. I typically get home, eat, log in and see what's up for MTTs on Stars that I like. If there's something appealing, I register for that and fire up a $5 or $10 SNG to go along with. Usually I can get through 3-4 SNGs during a good MTT. Obviously this depends on where I decide to suck for the night, in MTTs or in SNGs. The other night I managed to take 7th out of 300+ in a PL Omaha-hi tourney on Stars, and I think I ran through 5 SNGs during that time. I did okay, cashed in 3 of them and the MTT, so it was a good night.
If I'm playing ring games, pretty strictly 2 tables unless I'm working off a bonus. I'm just not that good yet, so two is about all I can pay enough attention to to be effective. I've seen a severe drop in EV if I add a 3rd table, or if I mix games in my ring games. It's pretty easy to keep the games straight in tourneys or SNGs, but I do not ever recommend playing Omaha and O8 at the same time, for obvious reasons.
I know a lot of folks look at 2 tables as a tiny number, but I often also wonder if those folks who play 4-8 tables at a time would be able to harvest more from the fishies if they played fewer tables and focused more?